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30secondsofcode
2019-03-19 07:46:09 +00:00
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7
README.md
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@ -4671,6 +4671,7 @@ const checkProp = (predicate, prop) => obj => !!predicate(obj[prop]);
```js ```js
const lengthIs4 = checkProp(l => l === 4, 'length'); const lengthIs4 = checkProp(l => l === 4, 'length');
lengthIs4([]); // false lengthIs4([]); // false
lengthIs4([1,2,3,4]); // true lengthIs4([1,2,3,4]); // true
@ -8873,17 +8874,19 @@ isNull(null); // true
Checks if the given argument is a number. Checks if the given argument is a number.
Use `typeof` to check if a value is classified as a number primitive. Use `typeof` to check if a value is classified as a number primitive.
To safeguard against `NaN`, check if `val === val` (as `NaN` has a `typeof` equal to `number` and is the only value not equal to itself).
```js ```js
const isNumber = val => typeof val === 'number'; const isNumber = val => typeof val === 'number' && val === val;
``` ```
<details> <details>
<summary>Examples</summary> <summary>Examples</summary>
```js ```js
isNumber('1'); // false
isNumber(1); // true isNumber(1); // true
isNumber('1'); // false
isNumber(NaN); // false
``` ```
</details> </details>

1
docs/function.html
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@ -146,6 +146,7 @@ console<span class="token punctuation">.</span><span class="token function">log<
</pre></div><div class="card code-card"><div class="corner beginner"></div><div class="section card-content"><h4 id="checkprop">checkProp</h4><p>Given a <code>predicate</code> function and a <code>prop</code> string, this curried function will then take an <code>object</code> to inspect by calling the property and passing it to the predicate.</p><p>Summon <code>prop</code> on <code>obj</code>, pass it to a provided <code>predicate</code> function and return a masked boolean.</p></div><div class="copy-button-container"><button class="copy-button" aria-label="Copy to clipboard"></button></div><pre class="section card-code language-js"><span class="token keyword">const</span> <span class="token function-variable function">checkProp</span> <span class="token operator">=</span> <span class="token punctuation">(</span>predicate<span class="token punctuation">,</span> prop<span class="token punctuation">)</span> <span class="token operator">=></span> obj <span class="token operator">=> !!</span><span class="token function">predicate</span><span class="token punctuation">(</span>obj<span class="token punctuation">[</span>prop<span class="token punctuation">]);</span> </pre></div><div class="card code-card"><div class="corner beginner"></div><div class="section card-content"><h4 id="checkprop">checkProp</h4><p>Given a <code>predicate</code> function and a <code>prop</code> string, this curried function will then take an <code>object</code> to inspect by calling the property and passing it to the predicate.</p><p>Summon <code>prop</code> on <code>obj</code>, pass it to a provided <code>predicate</code> function and return a masked boolean.</p></div><div class="copy-button-container"><button class="copy-button" aria-label="Copy to clipboard"></button></div><pre class="section card-code language-js"><span class="token keyword">const</span> <span class="token function-variable function">checkProp</span> <span class="token operator">=</span> <span class="token punctuation">(</span>predicate<span class="token punctuation">,</span> prop<span class="token punctuation">)</span> <span class="token operator">=></span> obj <span class="token operator">=> !!</span><span class="token function">predicate</span><span class="token punctuation">(</span>obj<span class="token punctuation">[</span>prop<span class="token punctuation">]);</span>
</pre><label class="collapse">examples</label><pre class="section card-examples language-js"> </pre><label class="collapse">examples</label><pre class="section card-examples language-js">
<span class="token keyword">const</span> lengthIs4 <span class="token operator">=</span> <span class="token function">checkProp</span><span class="token punctuation">(</span>l <span class="token operator">=></span> l <span class="token operator">===</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token string">'length'</span><span class="token punctuation">);</span> <span class="token keyword">const</span> lengthIs4 <span class="token operator">=</span> <span class="token function">checkProp</span><span class="token punctuation">(</span>l <span class="token operator">=></span> l <span class="token operator">===</span> <span class="token number">4</span><span class="token punctuation">,</span> <span class="token string">'length'</span><span class="token punctuation">);</span>
<span class="token function">lengthIs4</span><span class="token punctuation">([]);</span> <span class="token comment">// false</span> <span class="token function">lengthIs4</span><span class="token punctuation">([]);</span> <span class="token comment">// false</span>
<span class="token function">lengthIs4</span><span class="token punctuation">([</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">4</span><span class="token punctuation">]);</span> <span class="token comment">// true</span> <span class="token function">lengthIs4</span><span class="token punctuation">([</span><span class="token number">1</span><span class="token punctuation">,</span><span class="token number">2</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">,</span><span class="token number">4</span><span class="token punctuation">]);</span> <span class="token comment">// true</span>

7
docs/type.html
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@ -136,9 +136,10 @@
<span class="token function">isNil</span><span class="token punctuation">(</span>undefined<span class="token punctuation">);</span> <span class="token comment">// true</span> <span class="token function">isNil</span><span class="token punctuation">(</span>undefined<span class="token punctuation">);</span> <span class="token comment">// true</span>
</pre></div><div class="card code-card"><div class="corner beginner"></div><div class="section card-content"><h4 id="isnull">isNull</h4><p>Returns <code>true</code> if the specified value is <code>null</code>, <code>false</code> otherwise.</p><p>Use the strict equality operator to check if the value and of <code>val</code> are equal to <code>null</code>.</p></div><div class="copy-button-container"><button class="copy-button" aria-label="Copy to clipboard"></button></div><pre class="section card-code language-js"><span class="token keyword">const</span> <span class="token function-variable function">isNull</span> <span class="token operator">=</span> val <span class="token operator">=></span> val <span class="token operator">===</span> <span class="token keyword">null</span><span class="token punctuation">;</span> </pre></div><div class="card code-card"><div class="corner beginner"></div><div class="section card-content"><h4 id="isnull">isNull</h4><p>Returns <code>true</code> if the specified value is <code>null</code>, <code>false</code> otherwise.</p><p>Use the strict equality operator to check if the value and of <code>val</code> are equal to <code>null</code>.</p></div><div class="copy-button-container"><button class="copy-button" aria-label="Copy to clipboard"></button></div><pre class="section card-code language-js"><span class="token keyword">const</span> <span class="token function-variable function">isNull</span> <span class="token operator">=</span> val <span class="token operator">=></span> val <span class="token operator">===</span> <span class="token keyword">null</span><span class="token punctuation">;</span>
</pre><label class="collapse">examples</label><pre class="section card-examples language-js"><span class="token function">isNull</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">);</span> <span class="token comment">// true</span> </pre><label class="collapse">examples</label><pre class="section card-examples language-js"><span class="token function">isNull</span><span class="token punctuation">(</span><span class="token keyword">null</span><span class="token punctuation">);</span> <span class="token comment">// true</span>
</pre></div><div class="card code-card"><div class="corner beginner"></div><div class="section card-content"><h4 id="isnumber">isNumber</h4><p>Checks if the given argument is a number.</p><p>Use <code>typeof</code> to check if a value is classified as a number primitive.</p></div><div class="copy-button-container"><button class="copy-button" aria-label="Copy to clipboard"></button></div><pre class="section card-code language-js"><span class="token keyword">const</span> <span class="token function-variable function">isNumber</span> <span class="token operator">=</span> val <span class="token operator">=></span> <span class="token keyword">typeof</span> val <span class="token operator">===</span> <span class="token string">'number'</span><span class="token punctuation">;</span> </pre></div><div class="card code-card"><div class="corner beginner"></div><div class="section card-content"><h4 id="isnumber">isNumber</h4><p>Checks if the given argument is a number.</p><p>Use <code>typeof</code> to check if a value is classified as a number primitive. To safeguard against <code>NaN</code>, check if <code>val === val</code> (as <code>NaN</code> has a <code>typeof</code> equal to <code>number</code> and is the only value not equal to itself).</p></div><div class="copy-button-container"><button class="copy-button" aria-label="Copy to clipboard"></button></div><pre class="section card-code language-js"><span class="token keyword">const</span> <span class="token function-variable function">isNumber</span> <span class="token operator">=</span> val <span class="token operator">=></span> <span class="token keyword">typeof</span> val <span class="token operator">===</span> <span class="token string">'number'</span> <span class="token operator">&amp;&amp;</span> val <span class="token operator">===</span> val<span class="token punctuation">;</span>
</pre><label class="collapse">examples</label><pre class="section card-examples language-js"><span class="token function">isNumber</span><span class="token punctuation">(</span><span class="token string">'1'</span><span class="token punctuation">);</span> <span class="token comment">// false</span> </pre><label class="collapse">examples</label><pre class="section card-examples language-js"><span class="token function">isNumber</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">);</span> <span class="token comment">// true</span>
<span class="token function">isNumber</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">);</span> <span class="token comment">// true</span> <span class="token function">isNumber</span><span class="token punctuation">(</span><span class="token string">'1'</span><span class="token punctuation">);</span> <span class="token comment">// false</span>
<span class="token function">isNumber</span><span class="token punctuation">(</span><span class="token number">NaN</span><span class="token punctuation">);</span> <span class="token comment">// false</span>
</pre></div><div class="card code-card"><div class="corner beginner"></div><div class="section card-content"><h4 id="isobject">isObject</h4><p>Returns a boolean determining if the passed value is an object or not.</p><p>Uses the <code>Object</code> constructor to create an object wrapper for the given value. If the value is <code>null</code> or <code>undefined</code>, create and return an empty object. Οtherwise, return an object of a type that corresponds to the given value.</p></div><div class="copy-button-container"><button class="copy-button" aria-label="Copy to clipboard"></button></div><pre class="section card-code language-js"><span class="token keyword">const</span> <span class="token function-variable function">isObject</span> <span class="token operator">=</span> obj <span class="token operator">=></span> obj <span class="token operator">===</span> <span class="token function">Object</span><span class="token punctuation">(</span>obj<span class="token punctuation">);</span> </pre></div><div class="card code-card"><div class="corner beginner"></div><div class="section card-content"><h4 id="isobject">isObject</h4><p>Returns a boolean determining if the passed value is an object or not.</p><p>Uses the <code>Object</code> constructor to create an object wrapper for the given value. If the value is <code>null</code> or <code>undefined</code>, create and return an empty object. Οtherwise, return an object of a type that corresponds to the given value.</p></div><div class="copy-button-container"><button class="copy-button" aria-label="Copy to clipboard"></button></div><pre class="section card-code language-js"><span class="token keyword">const</span> <span class="token function-variable function">isObject</span> <span class="token operator">=</span> obj <span class="token operator">=></span> obj <span class="token operator">===</span> <span class="token function">Object</span><span class="token punctuation">(</span>obj<span class="token punctuation">);</span>
</pre><label class="collapse">examples</label><pre class="section card-examples language-js"><span class="token function">isObject</span><span class="token punctuation">([</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">]);</span> <span class="token comment">// true</span> </pre><label class="collapse">examples</label><pre class="section card-examples language-js"><span class="token function">isObject</span><span class="token punctuation">([</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">]);</span> <span class="token comment">// true</span>
<span class="token function">isObject</span><span class="token punctuation">([]);</span> <span class="token comment">// true</span> <span class="token function">isObject</span><span class="token punctuation">([]);</span> <span class="token comment">// true</span>

1
snippets/checkProp.md
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@ -11,6 +11,7 @@ const checkProp = (predicate, prop) => obj => !!predicate(obj[prop]);
```js ```js
const lengthIs4 = checkProp(l => l === 4, 'length'); const lengthIs4 = checkProp(l => l === 4, 'length');
lengthIs4([]); // false lengthIs4([]); // false
lengthIs4([1,2,3,4]); // true lengthIs4([1,2,3,4]); // true

2
test/_30s.js
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@ -604,7 +604,7 @@ const isLowerCase = str => str === str.toLowerCase();
const isNegativeZero = val => val === 0 && 1 / val === -Infinity; const isNegativeZero = val => val === 0 && 1 / val === -Infinity;
const isNil = val => val === undefined || val === null; const isNil = val => val === undefined || val === null;
const isNull = val => val === null; const isNull = val => val === null;
const isNumber = val => typeof val === 'number'; const isNumber = val => typeof val === 'number' && val === val;
const isObject = obj => obj === Object(obj); const isObject = obj => obj === Object(obj);
const isObjectLike = val => val !== null && typeof val === 'object'; const isObjectLike = val => val !== null && typeof val === 'object';
const isPlainObject = val => !!val && typeof val === 'object' && val.constructor === Object; const isPlainObject = val => !!val && typeof val === 'object' && val.constructor === Object;