有时文件名是编号的，其中索引可能在开头或结尾。所以我想从弦的中心开始缩短:

function stringTruncateFromCenter(str, maxLength) {
    const midChar = "…";      // character to insert into the center of the result
    var left, right;

    if (str.length <= maxLength) return str;

    // length of beginning part      
    left = Math.ceil(maxLength / 2);

    // start index of ending part   
    right = str.length - Math.floor(maxLength / 2) + 1;   

    return str.substr(0, left) + midChar + str.substring(right);
}

请注意，我在这里使用了UTF-8中超过1个字节的填充字符。

我在谷歌上快速搜索了一下，发现了这个……这对你有用吗?

/**
 * Truncate a string to the given length, breaking at word boundaries and adding an elipsis
 * @param string str String to be truncated
 * @param integer limit Max length of the string
 * @return string
 */
var truncate = function (str, limit) {
    var bits, i;
    if (STR !== typeof str) {
        return '';
    }
    bits = str.split('');
    if (bits.length > limit) {
        for (i = bits.length - 1; i > -1; --i) {
            if (i > limit) {
                bits.length = i;
            }
            else if (' ' === bits[i]) {
                bits.length = i;
                break;
            }
        }
        bits.push('...');
    }
    return bits.join('');
};
// END: truncate

我不确定这是否算聪明，但它简洁明了:

truncateStringToLength (string, length) {
  return (string.length > length)
    ? `${string.substring(0, length)} …`
    : string
}

……然后:

truncateStringToLength('Lorem ipsum dolor sit amet, consetetur sadipscing', 20)

在我看来，C_harm的答案是最好的。请注意，如果你想使用

"My string".truncate(n)

您将不得不使用regexp对象构造函数而不是文字。此外，在转换\S时还必须转义它。

String.prototype.truncate =
    function(n){
        var p  = new RegExp("^.{0," + n + "}[\\S]*", 'g');
        var re = this.match(p);
        var l  = re[0].length;
        var re = re[0].replace(/\s$/,'');

        if (l < this.length) return re + '&hellip;';
    };

聪明的地方:D

//My Huge Huge String let tooHugeToHandle = `It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).` //Trim Max Length const maxValue = 50 // The barber. const TrimMyString = (string, maxLength, start = 0) => { //Note - `start` is if I want to start after some point of the string if (string.length > maxLength) { let trimmedString = string.substr(start, maxLength) return ( trimmedString.substr( start, Math.min(trimmedString.length, trimmedString.lastIndexOf(' ')) ) + ' ...' ) } return string } console.log(TrimMyString(tooHugeToHandle, maxValue))

我喜欢使用.slice()，第一个参数是开始索引，第二个是结束索引。介于两者之间的都是你能得到的。

var long = "hello there! Good day to ya."
// hello there! Good day to ya.

var short  = long.slice(0, 5)
// hello