Javascript 如何在Javascript中将字符串修剪为N个字符？

How to trim a string to N chars in Javascript?

提问by Will

How can I, using Javascript, make a function that will trim string passed as argument, to a specified length, also passed as argument. For example:

我如何使用 Javascript 制作一个函数，将作为参数传递的字符串修剪为指定长度，也作为参数传递。例如：

var string = "this is a string";
var length = 6;
var trimmedString = trimFunction(length, string);

// trimmedString should be:
// "this is"

Anyone got ideas? I've heard something about using substring, but didn't quite understand.

有人有想法吗？我听说过使用 substring 的东西，但不太明白。

回答by Will

Why not just use substring... string.substring(0, 7);The first argument (0) is the starting point. The second argument (7) is the ending point (exclusive). More info here.

为什么不直接使用子字符串...string.substring(0, 7);第一个参数 (0) 是起点。第二个参数 (7) 是终点（不包括）。更多信息在这里。

var string = "this is a string";
var length = 7;
var trimmedString = string.substring(0, length);

回答by Jon Lauridsen

Copying Will'scomment into an answer, because I found it useful:

将Will 的评论复制到答案中，因为我发现它很有用：

var string = "this is a string";
var length = 20;
var trimmedString = string.length > length ? 
                    string.substring(0, length - 3) + "..." : 
                    string;

Thanks Will.

谢谢威尔。

And a jsfiddle for anyone who cares https://jsfiddle.net/t354gw7e/:)

对于任何关心https://jsfiddle.net/t354gw7e/ 的人来说，这是一个 jsfiddle :)

回答by xameeramir

I suggest to use an extension for code neatness. Note that extending an internal object prototype could potentially mess with libraries that depend on them.

我建议使用扩展来保持代码整洁。请注意，扩展内部对象原型可能会干扰依赖它们的库。

String.prototype.trimEllip = function (length) {
  return this.length > length ? this.substring(0, length) + "..." : this;
}

And use it like:

并像这样使用它：

var stringObject= 'this is a verrrryyyyyyyyyyyyyyyyyyyyyyyyyyyyylllooooooooooooonggggggggggggsssssssssssssttttttttttrrrrrrrrriiiiiiiiiiinnnnnnnnnnnnggggggggg';
stringObject.trimEllip(25)

回答by kendaleiv

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/String/substr

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/String/substr

From link:

来自链接：

string.substr(start[, length])

回答by Matthew Egan

Little late... I had to respond. This is the simplest way.

有点晚了......我不得不回应。这是最简单的方法。

// JavaScript
function fixedSize_JS(value, size) {
  return value.padEnd(size).substring(0, size);
}

// JavaScript (Alt)
var fixedSize_JSAlt = function(value, size) {
  return value.padEnd(size).substring(0, size);
}

// Prototype (preferred)
String.prototype.fixedSize = function(size) {
  return this.padEnd(size).substring(0, size);
}

// Overloaded Prototype
function fixedSize(value, size) {
  return value.fixedSize(size);
}

// usage
console.log('Old school JS -> "' + fixedSize_JS('test (30 characters)', 30) + '"');
console.log('Semi-Old school JS -> "' + fixedSize_JSAlt('test (10 characters)', 10) + '"');
console.log('Prototypes (Preferred) -> "' + 'test (25 characters)'.fixedSize(25) + '"');
console.log('Overloaded Prototype (Legacy support) -> "' + fixedSize('test (15 characters)', 15) + '"');

Step by step. .padEnd - Guarentees the length of the string

一步步。.padEnd - 保证字符串的长度

"The padEnd() method pads the current string with a given string (repeated, if needed) so that the resulting string reaches a given length. The padding is applied from the end (right) of the current string. The source for this interactive example is stored in a GitHub repository." source: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

“padEnd() 方法用给定的字符串填充当前字符串（重复，如果需要），以便结果字符串达到给定的长度。填充是从当前字符串的末尾（右侧）应用的。此交互式的源示例存储在 GitHub 存储库中。” 来源：developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/...

.substring - limits to the length you need

.substring - 限制你需要的长度

If you choose to add ellipses, append them to the output.

如果您选择添加省略号，请将它们附加到输出中。

I gave 4 examples of common JavaScript usages. I highly recommend using the String prototype with Overloading for legacy support. It makes it much easier to implement and change later.

我给出了 4 个常见的 JavaScript 用法示例。我强烈建议使用带有重载的 String 原型来获得遗留支持。它使以后实施和更改变得更加容易。

回答by MD. ABU TALHA

    let trimString = function (string, length) {
      return string.length > length ? 
             string.substring(0, length) + '...' :
             string;
    };

Use Case,

用例，

let string = 'How to trim a string to N chars in Javascript';

trimString(string, 20);

//How to trim a string...

回答by Babak

I think that you should use this code :-)

我认为您应该使用此代码:-)

    // sample string
            const param= "Hi you know anybody like pizaa";

         // You can change limit parameter(up to you)
         const checkTitle = (str, limit = 17) => {
      var newTitle = [];
      if (param.length >= limit) {
        param.split(" ").reduce((acc, cur) => {
          if (acc + cur.length <= limit) {
            newTitle.push(cur);
          }
          return acc + cur.length;
        }, 0);
        return `${newTitle.join(" ")} ...`;
      }
      return param;
    };
    console.log(checkTitle(str));

// result : Hi you know anybody ...