事实上,主要的 JavaScript 框架(比如 jQuery、Underscore 和 Prototype 等等)都有安全和通用的 for-each 功能实现。 在JSLint 的 for in 章节里面也提到,for in 语句允许循环遍历对象的属性名,但是也会遍历到那些通过原型链继承下来的属性,这在很多情况下都会造成预期以外的错误。有一种粗暴的解决办法: 代码语言:...
而for循环可以通过break语句提前退出,并且可以定义一个明确的返回值。 不能使用return跳出循环:在forEach中,无法使用return语句来中断循环,而在for循环中可以通过break来实现。 遍历对象属性:forEach只能用于数组,而for...in循环可以用于遍历对象属性。但需要注意,for...in循环还会遍历原型链上的属性,可能不是你期望的...
var x = 1;document.write("Entering the loop ");while (x < 20){ if (x == 5){ break; // breaks out of loop completely } x = x + 1; document.write( x + "");}document.write("Exiting the loop! ");这将产生以下结果：Entering the loop Exiting the loop!已经看到b...
In JavaScript, the for loop is used for iterating over a block of code a certain number of times, or to iterate over the elements of an array. Here's a quick example of the for loop. You can read the rest of the tutorial for more details. Example for (let i = 0; i < 3; i...
JavaScript for LoopLearning outcomes: Introduction to loops What is the for loop meant for Syntax of for Basic for loop examples Nested for loops The break and continue keywords The return keyword Introduction Loops, also known as loop statements or iteration statements, are amongst those ideas in...
如此循环就形成了 event loop,其中,每轮执行一个宏任务和所有的微任务。 浏览器通常会尝试每秒渲染 60 次页面,以达到每秒 60 帧(60 fps)的速度。在页面渲染时,任何任务都无法再进行修改。 如果想要实现平滑流畅的应用,单个任务和该任务附属的所有微任务,都应在 16ms 内完成。
Usingletin a loop: Example leti =5; for(leti =0; i <10; i++) { // some code } // Here i is 5 Try it Yourself » In the first example, usingvar, the variable declared in the loop redeclares the variable outside the loop. ...
This code snippet prints out the value of the i variable, and increments it by one. When the value of i reaches 3, it breaks out of the loop. That is how thebreak;expression operates. forloops andcontinue; Thecontinue;expression is similar tobreak;only this one only breaks out of the...
Thebreakstatement can also be used to jump out of a loop: Example for(leti =0; i <10; i++) { if(i ===3) {break; } text +="The number is "+ i +""; } Try it Yourself » In the example above, thebreakstatement ends the loop ("breaks" the loop) when the loop counter...
The Break Statement The break statement can be used to jump out of a loop or a switch() statement. Thebreak statementbreaks the loop and continues executing the code after the loop (if any): Example for(i=0;i<10;i++) {if(i==3) ...