let array = [1, 2, 3, 4];functionemptyArray() { array = [];}emptyArray(); 但是,这有一个效率更高的方法来清空副本。你可以这样写: let array = [1, 2, 3, 4];functionemptyArray() { array.length = 0;}emptyArray(); 拍平多维矩阵 使用...运算符,将多维尺寸拍平: const arr = [1...
console.log(example(arr,'age'));//object: {18: Array(3), 19: Array(2), 20: Array(2)}18: Array(3)0: {name: "小孙", age: 18, score: 60, weight: 60}1: {name: "小李", age: 18, score: 60, weight: 70}2: {name: "小赵", age: 18, score: 60, weight: 60}19: Arr...
isType(obj); // "Object" isType(a) // "Array" 但是,很多时候我们在处理数据的时候,需要判断一个对象是否为{}: var isEmptyObject = function(obj) { for (var name in obj) { return false; } return true; }; isEmptyObject({}); // true isEmptyObject({name: 'xzavier'}); //false ...
// [40, 60].findIndex(40 => 50 <= 40) --> falsy // [40, 60].findIndex(60 => 50 <= 60) --> truthy // returns 1 because num would fit like so [40, 50, 60] // Return the correct index of num. // If num belongs at the end of sortedArray or if arr is empty //...
Tests whether all elements in an array are truthy. var x = [ 1, 2, 3, 4 ]; var bool = every( x ); // returns trueNotes If provided an empty array, the function returns true. The function does not skip undefined elements and is thus not optimized for sparse arrays.Examples...
If a predicate function does not return a truthy value for any array element, the method returns an empty array. function predicate( v ) { return ( v >= 10 ); } var arr1 = new Uint32Array( [ 1, 2, 3 ] ); var arr2 = arr1.filter( predicate ); // returns <Uint32Array>[]...
...下面这个例子是数值项求平方: var data = [1, 2, 3, 4]; var arrayOfSquares = data.map(function (item) { return item...方法: if (typeof Array.prototype.map ! 7.2K20 JS 中为啥 .map(parseInt) 返回 尝试使用map和parseInt将字符串数组转换为整数。...真值(truthy) & 虚值(falsy) 以下...
function isEmpty(obj) { return Reflect.ownKeys(obj).length === 0 && obj.constructor === Object; } 1. 2. 3. 12.克隆数组 let arr = [25, 7.145, 7.2, 120, 40, 56]; const clone = (arr) => arr.slice(0); const clone = (arr) => [...arr]; ...
Given a set of key names, gets the value of the first key found to be truthy. The key names can be given as separate arguments or as an array. If the last argument is a function, it will be called with the result; otherwise, the value is returned. ...
A value such as['mango', 'pineapple']is an array type, but in JS an array type can also be considered akind of object, and akind of truthyvalue. An empty string""is a string typebut also akind of falsyvalue, and even though everything or almost everything is an object in JS, ...