for (const key in arr) { console.log(key) } // 0,1,2,3,4 使用for...in可以遍历数组,但是会存在以下问题: index 索引为字符串型数字(注意,非数字),不能直接进行几何运算。 遍历顺序有可能不是按照实际数组的内部顺序(可能按照随机顺序)。 所以一般不建议使用for...in来遍历数组。 for...of for....
If statement 2 returns true, the loop will start over again, if it returns false, the loop will end.If you omit statement 2, you must provide a break inside the loop. Otherwise the loop will never end. This will crash your browser. Read about breaks in a later chapter of this ...
letkey;constarr = [];arr[0] = “a”;arr[100] = “b”;arr[10000] = “c”;for(keyinarr) {if(arr.hasOwnProperty(key) &&/⁰$|^[1–9]\d*$/.test(key) &&key <=4294967294) {console.log(arr[key]);}} For-in 仅遍历现有实体。上例中f...
for-in 循环遍历的是对象的属性,而不是数组的索引。因此, for-in 遍历的对象不局限于数组,还可以遍历对象。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 constperson={fname:"san",lname:"zhang",age:29};letinfo;for(infoinperson){console.log("person["+info+"] = "+person[info]);}// ...
JavaScript for loop JavaScript for...in loop JavaScript for...of loop Thefor...ofloop was introduced in the later versions ofJavaScript ES6. Thefor..ofloop in JavaScript allows you to iterate over iterable objects (arrays, sets, maps, strings etc). ...
If expression 2 returns true, the loop will start over again. If it returns false, the loop will end.Note If you omit expression 2, you must provide a break inside the loop. Otherwise the loop will never end. This will crash your browser. Read about breaks in a later chapter of this...
In this chapter, we start off by exploring all the nitty gritty details of the for loop, followed by those of while in the next chapter. Let's begin. What is for meant for? So what is for meant for? Well, precisely speaking: The for loop is meant to repeatedly execute a piece of...
for...in循环仅打印了iterable对象的可枚举属性。它不会打印数组中的元素3、5、7或"hello",因为它们不是属性,而是值。它打印了数组的索引以及arrCustom和objCustom,它们是实际的属性。如果你对为什么迭代这些属性感到困惑,可以查看关于数组迭代和for...in工作原理的更详细解释。
JavaScript for...in Loop ❮PreviousJavaScriptStatementsNext❯ Examples Iterate (loop) over the properties of an object: constperson = {fname:"John", lname:"Doe", age:25}; lettext =""; for(letxinperson) { text += person[x] +" ";...
这时候 Eslint 又报了错:no-await-in-loop 。关于这一点,Eslint 官方文档 https://eslint.org/docs/rules/no-await-in-loop 也做了说明。 好的写法: async function foo(things) { const results = []; for (const thing of things) { // Good: all asynchronous operations are immediately started....