array.keys() : 包含原始数组的键名(key), 键名的遍历器对象,可以用 for...of 循环进行遍历。 array.values() : 包含原始数组的键值(value), 键值的遍历器对象,可以用 for...of 循环进行遍历。 array.entries() : 包含原始数组的键名(key)、键值(value),键值对的遍历器对象,可以用 for...of 循环进行...
[].map();基本用法跟forEach方法类似:array.map(callback,[ thisObject]);callback的参数也类似:[].map(function(value, index, array) { // … });map方法的作用不难理解,“映射”嘛,也就是原数组被“映射”成对应新数组。下面这个例子是数值项求平方:var data = [1, 2, 3, 4]; var arrayOfSqu...
10.Array.forEach(fn, thisValue)thisValue可传可不传,决定在fn用this指向 -+-对数组中的每个元素运行给定函数。这个方法没有返回值。这里fn是可以传3个参数function(currentValue:必传当前元素,index:可选当前元素的索引值,arr:可选当前元素所属的数组对象) 1 2 3 4 5 6 7 letmyArr = [1,5,8] myAr...
function clamp(value,min,max) {returnMath.min(Math.max(value,min),max);} 7. Object 因为typeof null === 'object' 是 JavaScript 版的恶意代码。 function isObject(val) {returnval&& typeofval==='object'&& !Array.isArray...
We are going to demonstrate two functions to search arrays. The first function will return1or0if a value that is passed exists in an array of simple values. If the value exists, the function will return1, and if the value does nto exist in the array, it will return0. Let’s look ...
JavaScript Array indexOf()The indexOf() method searches an array for an element value and returns its position.Note: The first item has position 0, the second item has position 1, and so on.Example Search an array for the item "Apple": const fruits = ["Apple", "Orange", "Apple", ...
Finding a value in an array is useful for effective data analysis. Learn how to discover what a JavaScript Array contains using indexOf, includes, for loop, some methods and more.
//code to check if a value exists in an array using javascript for loop var fruits_arr = ['Apple', 'Mango', 'Grapes', 'Orange', 'Fig', 'Cherry']; function checkValue(value, arr) { var status = 'Not exist'; for (var i = 0; i < arr.length; i++) { var name = arr[...
functionmyFunction(value, index, array) { returnvalue >18; } Try it Yourself » Note that the function takes 3 arguments: The item value The item index The array itself In the example above, the callback function does not use the index and array parameters, so they can be omitted: ...
Array.prototype.reduceRight() JavaScript 1.8功能更新 对for..in解构的修改 JavaScript1.8中的一个修改是对JavaScript1.7中引入的数组键值结构相关的bug修复。之前可以用for ( var [key, value] in array )的方式来解构一个数组的键值。但是,这也让对数组的数组的键值解构变得不可能(比如一个迭代器返回一个当前键...