16 lines
592 B
Markdown
16 lines
592 B
Markdown
---
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title: defaults
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tags: object,intermediate
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---
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Assigns default values for all properties in an object that are `undefined`.
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- Use `Object.assign()` to create a new empty object and copy the original one to maintain key order, use `Array.prototype.reverse()` and the spread operator `...` to combine the default values from left to right, finally use `obj` again to overwrite properties that originally had a value.
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```js
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const defaults = (obj, ...defs) => Object.assign({}, obj, ...defs.reverse(), obj);
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```
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```js
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defaults({ a: 1 }, { b: 2 }, { b: 6 }, { a: 3 }); // { a: 1, b: 2 }
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``` |