Question

我很困惑。为什么在下面的代码块中i + = 1打印输出12x，但是i + = 2只打印6次？不应该这样吗？（我的大脑今天不工作。）

function printManyTimes(str) {
  "use strict";

  const SENTENCE = str + " is cool!";

  for (let i = 0; i < str.length; i += 2 ) {
    console.log(SENTENCE);
  }
}

printManyTimes("freeCodeCamp");

Answer 1

当i小于 str.length时循环。

如果您将i的增加速度提高一倍，那么它会变成str.length的一半时间。

Answer 2

因为您每次迭代都将迭代器推进两个单元

Answer 3

此处是代码的修改版本，用于显示 for循环的工作方式。昆汀的回答很好地解释了这一点。

function printManyTimes(str, amountToIncrement) {
  "use strict";

  const SENTENCE = str + " is cool!";

  for (let i = 0; i < str.length; i += amountToIncrement ) {
    console.log(SENTENCE + " " + i);
  }
}

console.log("increment amount as 1")
printManyTimes("freeCodeCamp", 1);

console.log("increment amount as 2")
printManyTimes("freeCodeCamp", 2);

console.log("increment amount as 3")
printManyTimes("freeCodeCamp", 3);

console.log("increment amount as .5")
printManyTimes("freeCodeCamp", .5);

Answer 4

function printManyTimes(str) {
  "use strict";

  const SENTENCE = str + " is cool!"; // freeCodeCamp is cool!

  for (let i = 0; i < str.length; i += 2 ) { 
    // if i+=2 in your loop the console log run only while i = [0, 2, 4, 6, 8, 10] - 6 times
    // if i+=1/i++ in your loop the console log run only while i = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11] - 12 times
    console.log(SENTENCE);
  }
}

printManyTimes("freeCodeCamp"); // freeCodeCamp length = 12

这是数组的基础知识。您可以在https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for

中找到更多信息。

为什么i + = 1使i + = 2的输出翻倍？

4 个答案: