Javascript:在没有长度属性和切片的情况下获取字符串的长度

Question

我知道，这很奇怪!但为什么这不起作用？

function getStringLength(string) {

  // see how many substrings > 0 can be built
  // log that number & return

  var subString = string.slice();
  var counter = 0;

  while (subString !== '') {
    counter++;
    subString = subString.slice(counter);
  }

  return counter;
}

var output = getStringLength('hello');

console.log(output); // --> expecting 5, but getting 3 (??)

我真的很想用切片来做!最初的挑战是不使用 length 属性，我想通了，效果很好:

function getStringLength(string) {

  var long = 0;

  while (string[long] !== undefined) {
    long++;
  }

  return long;
}

Answer 1

你正在改变你的字符串，这应该对你有用

function getStringLength(string) {

  // see how many substrings > 0 can be built
  // log that number & return

  var subString = string.slice();
  var counter = 0;

  while (subString !== '') {
    counter++;
    subString = subString.slice(1);
  }

  return counter;
}

var output = getStringLength('hello');

console.log(output); // 5

主要区别在于我在做

subString = subString.slice(1);

代替

subString = subString.slice(counter);

总是将长度减 1