JS 数组移除元素
1. Remove all undefined values
An undefined value automatically gets assigned in JavaScript where no value has been explicitly assigned. To remove all undefined values from the array, we can use the filter() method.
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var arr = [ 0, 1, '', undefined, false, 2, undefined, null, , 3 ];
var filtered = arr.filter(function(x) {
return x !== undefined;
});
console.log(filtered);
/*
Output: [ 0, 1, '', false, 2, null, 3]
*/
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Here’s version using lamdba expressions:
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var arr = [ 0, 1, '', undefined, false, 2, undefined, null, , 3 ];
var filtered = arr.filter(x => x !== undefined);
console.log(filtered);
/*
Output: [ 0, 1, '', false, 2, null, 3]
*/
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2. Remove all nullish values
A nullish value is either null or undefined. To filters all nullish values from the array, we can use the != operator:
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var arr = [ 0, 1, '', undefined, false, 2, undefined, null, , 3, NaN ];
var filtered = arr.filter(e => e != null);
console.log(filtered);
/*
Output: [ 0, 1, '', false, 2, 3, NaN ]
*/
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3. Remove all holes
To remove all holes from an array, the idea is to call the filter() method with callback function that returns true. Note that this approach only remove holes from the array but doesn’t remove any of the other falsy values.
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var arr = [0, , , 1, , , , , 2, , , , 3];
var filtered = arr.filter(() => true);
console.log(filtered);
/*
Output: [ 0, 1, 2, 3 ]
*/
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4. Remove all falsy values
There are 7 falsy values in JavaScript – false, zero (0), BigInt (0n), empty string ("", '', ``), null, undefined, and NaN. To filter out all the falsy values from the array, we can pass Boolean constructor to the filter() method:
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var arr = [ 0, 1, '', undefined, false, 2, undefined, null, , 3, NaN ];
var filtered = arr.filter(Boolean);
console.log(filtered);
/*
Output: [ 1, 2, 3 ]
*/
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