40 lines
1021 B
Markdown
40 lines
1021 B
Markdown
---
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title: hasKey
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tags: object,intermediate
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---
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Checks if the target value exists in a JSON object.
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- Check if `keys` is non-empty and use `Array.prototype.every()` to sequentially check its keys to internal depth of the object, `obj`.
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- Use `Object.prototype.hasOwnProperty()` to check if `obj` does not have the current key or is not an object, stop propagation and return `false`.
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- Otherwise assign the key's value to `obj` to use on the next iteration.
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- Return `false` beforehand if given key list is empty.
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```js
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const hasKey = (obj, keys) => {
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return (
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keys.length > 0 &&
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keys.every(key => {
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if (typeof obj !== 'object' || !obj.hasOwnProperty(key)) return false;
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obj = obj[key];
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return true;
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})
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);
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};
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```
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```js
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let obj = {
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a: 1,
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b: { c: 4 },
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'b.d': 5
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};
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hasKey(obj, ['a']); // true
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hasKey(obj, ['b']); // true
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hasKey(obj, ['b', 'c']); // true
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hasKey(obj, ['b.d']); // true
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hasKey(obj, ['d']); // false
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hasKey(obj, ['c']); // false
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hasKey(obj, ['b', 'f']); // false
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```
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