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 (??)

我真的想用切片来做！最初的挑战是不使用长度属性，我想出来了，这很好用：

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，这应该适合你

＆＃13;

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

＆＃13;

主要区别在于我在做什么

subString = subString.slice(1);

而不是

subString = subString.slice(counter);

总是将长度减少1

Answer 2

问题是代码import App from './App'; import Home from './Home'; import Contact from './Contact'; import About from './About'; ReactDOM.render( ( <Router history = {history}> <Route path = "/" component = {App}> <IndexRoute component = {Home} /> <Route path = "/home" component = {Home} /> <Route path = "/about" component = {About} /> <Route path = "/contact" component = {Contact} /> </Route> </Router> ), document.getElementById('app'));第一次，你砍掉1个字符。然后你从已经被砍掉的子串中砍下2个字符。要么一次切断1个，要么从原始字符串中切断增加的量。那就是substring.slice(counter)或substring.slice(1)

＆＃13;
＆＃13;
string.slice(counter)
＆＃13;
＆＃13;
＆＃13;

Answer 3

要达到预期效果，请使用以下选项

function getStringLength(arr){
  return arr.lastIndexOf(arr.slice(-1))+1
}

var output = getStringLength('hello');
console.log(output);

https://codepen.io/nagasai/pen/gGPWEE?editors=1111

选项2：由于数组类型为object，因此下面的选项也适用

function getStringLength(arr){
  return Object.keys(arr).pop()*1 + 1
}

var output = getStringLength('hello');
console.log(output);

https://codepen.io/nagasai/pen/PJZmgg?editors=1111

检查以下更新的选项以处理空和数字 https://codepen.io/nagasai/pen/GMoQgy?editors=1111
https://codepen.io/nagasai/pen/YrweWr?editors=1111

Answer 4

也许是一个稍微简短的回答：

＆＃13;

dat <- structure(list(Group = c(1L, 1L, 1L, 2L, 2L, 3L), ID = c("A", 
"A", "B", "A", "B", "C")), .Names = c("Group", "ID"), class = "data.frame", row.names = c(NA, 
-6L))

＆＃13;

Javascript：获取没有长度属性的字符串的长度，以及切片

4 个答案: