value) {// 数组检查valueif (Array.isArray(array)) {for (let index in array) {if (array[index] == value) {return true;}}}// 对象检查keyelse {for (let index in array) {if (index == value) {return true;}}}return false;}// 作用于数组console.log(inArray...
数组检查value, 对象检查key /** * 自定义成员检查函数 * @param {List/Object} array * @param {非引用类型} value */ function inArray(array, value) { // 数组检查value if (Array.isArray(array)) { for (let index in array) { if (array[index] == value) { return true; } } } // ...
includes method regards all value NaN (Not a Number) as equal. const arr = [NaN]; arr.includes(NaN); // true arr.indexOf(NaN); // -1 indexOf cannot be used to check for NaN values inside an array, but the includes method allows us to check if a NaN value exists inside an...
程序1: // Taking input as an array A// having some elements.varA = [1,2,3,4,5];//includes() method is called to// test whether the searching element// is present in given array or not.a = A.includes(2)// Printing result ofincludes().document.write(a); 输出: true 程序2: /...
Theincludes()method is case sensitive. Syntax array.includes(element,start) Parameters ParameterDescription elementRequired. The value to search for. startOptional. Start position. Default is 0. Return Value TypeDescription A booleantrueif the value is found, otherwisefalse. ...
The includes() method in React.js is used to determine if an element exists in an array. It returns a boolean value indicating whether the element is present or not. By default, it checks the entire array for the element's existence
methodsToPatch.forEach(function (method) { // cache original method /*将数组的原生方法缓存起来,后面要调用*/ const original = arrayProto[method] def(arrayMethods, method, function mutator (...args) { /*调用原生的数组方法*/ const result = original.apply(this, args) ...
The JavaScript Array.protoype.includes() method is used to check if an array contains a given element or not. Following is the code for the Array.protoype.includes() method − Example Live Demo <!DOCTYPE html> Document body { font-family: "Segoe UI", Tahoma, Geneva, Verdana...
In JavaScript, the method Array.includes() is a pre-defined function that determines if a specified item is present in an array. When the specified value is present in the array, the method returns true, otherwise, it returns false. The Array.includes() method is case-sensitive, treating ...
Introduction to the JavaScript includes() Method Theincludes()method is a built-in JavaScript function that checks if a specific element or substring is present in an array or a string, respectively. It returns a boolean value:trueif the element or substring is found andfalseif it is not. ...