String simple size / limit / html / text

string-limit.js

// usage
// var s = "This is a 非常长的字符串This is a 非常长的字符串This is a 非常长的字符串This is a 非常长的字符串";
// document.write(s.limit(20));

// character length
  String.prototype.size = function() {
    var s = this, n = 0; // [u4e00-u9fa5] chinese
    if(s) n = s.replace(/[^\x00-\xff]/g, "**").length;
    return n;
  };
  // limit trim postfix with ...
  String.prototype.limit = function(n, ishtml) {
    var s = (ishtml&&this.length>0?this.html():this);
    if(s && s.size() > n) {
        var l = s.length, u = s.substr(0, n>l?l-3:n-3);
        if(u.size() < n-3) u = s.substr(0, n-2);
        return "<span title=\""+this.replace(/\"/g,'&quot;')+"\">" +(ishtml?u.text():u) +"..." +"</span>";
    } else {
        return ishtml?s.text():s;
    }
  };
  var parser = document.createElement('div');

  // unescape html text (&amp; => &)
  String.prototype.html = function() {
    if(this.length==0) return this;
    var o = parser; o.innerHTML = this;
    return (o.innerText === undefined? o.textContent: o.innerText);
  };
  String.prototype.text = function() {
    if(this.length==0) return this;
    var o = parser; if(o.innerText === undefined) o.textContent = this; else o.innerText = this;
    return o.innerHTML;
  };