Java脚本for循环

Question

我希望循环运行到提示符的值，但它是无限的。需要帮助。以下是我的javascript代码：我的代码

var round = prompt("enter text");
var roundno = round;

var images_arr = ["../img/paper.png", "../img/stone.png", "../img/sisor.png"];
var size = images_arr.length
function myFunction() {
for (var i = 0; i = roundno; i + 1) {
    console.log(i);
    setInterval(function () {
        var x = Math.floor(size * Math.random())
        $('#random').attr('src', images_arr[x]);
    }, 1500);

    setInterval(function () {
        var sound = new Audio("../audio/audio.mp3");
        sound.play();
    }, 3000);

    if (i = roundno) {
        break;
     }
    }
  }

Answer 1

您的代码有很多问题。

var round = prompt("enter text"); // how do you know the user enters a number?
var defaultNumberOfRounds = 1;  // I added this row

// CHANGED THIS IN EDIT 
var roundno = round; // should be: isNaN(Number(round)) ? defaultNumberOfRounds : round

var images_arr = ["../img/paper.png", "../img/stone.png", "../img/sisor.png"];
var size = images_arr.length
function myFunction() {

// CHANGED THIS IN EDIT the conditions within () should be: var i = 0; i < roundno; i++
for (var i = 0; i = roundno; i + 1) {
    console.log(i);

    // all iterations in the loop will execute this at the same time.
    setInterval(function () {
        var x = Math.floor(size * Math.random())
        $('#random').attr('src', images_arr[x]); // JQuery
    }, 1500);

    // all iterations in the loop will execute this at the same time.
    setInterval(function () {
        var sound = new Audio("../audio/audio.mp3");
        sound.play();
    }, 3000);

    if (i = roundno) { // should be i == roundno
        break; // don't need to break it, because your for loop's condition should take care of this
     }
    }
  }
} // ADDED THIS IN EDIT: missing curly bracket

编辑:我添加了一个代码段，以显示我的代码正在工作。我注释了for循环中的所有代码，并且必须更改声明roundno和for循环中的语句。

​

var round = prompt("enter text");
var defaultNumberOfRounds = 1;
var roundno = isNaN(Number(round)) ? defaultNumberOfRounds : round;
var images_arr = ["../img/paper.png", "../img/stone.png", "../img/sisor.png"];
var size = images_arr.length;
console.log(`round: ${round}, roundno: ${roundno}`);
function myFunction() {
  for (var i = 0; i < roundno; i++) {
    console.log(i);

    /*setInterval(function () {
        var x = Math.floor(size * Math.random())
        $('#random').attr('src', images_arr[x]); // JQuery
    }, 1500);

    setInterval(function () {
        var sound = new Audio("../audio/audio.mp3");
        sound.play();
    }, 3000);*/

  }
}

myFunction();

​

Answer 2

您没有递增i

变化

i + 1

致下列之一：

• i++
• i += 1
• i = i + 1

此外，您还需要修复循环末尾的if语句。您希望检查i是否等于roundno。不要使用赋值操作符= (将roundno的值赋值给i )，而是使用==或===进行等式检查。

if (i == roundno) {
   break;
}

您也在循环条件下输入了相同的错误。将循环条件更改为i == roundno，并在循环结束时删除if语句，因为在循环条件固定后，循环中的if语句是不必要的。

for (var i = 0; i == roundno; i++) {
   // code
}