非标准
该特性是非标准的，请尽量不要在生产环境中使用它！
trimLeft() 方法从一个字符串的左端移除空白字符。string.trimLeft()trimLeft方法移除原字符串左端的连续空白符并返回,trimLeft方法并不会直接修改原字符串本身.
trimLeft下面的例子输出了小写的字符串"foo ":
var str = " foo "; alert(str.length); // 8 str = str.trimLeft(); alert(str.length); // 5 document.write( str );
StringString.fromCharCode()String.fromCodePoint()String.prototype.anchor()String.prototype.big()String.prototype.blink()String.prototype.bold()String.prototype.charAt()String.prototype.charCodeAt()String.prototype.codePointAt()String.prototype.concat()String.prototype.endsWith()String.prototype.fixed()String.prototype.fontcolor()String.prototype.fontsize()String.prototype.includes()String.prototype.indexOf()String.prototype.italics()String.prototype.lastIndexOf()String.prototype.link()String.prototype.localeCompare()String.prototype.match()String.prototype.normalize()String.prototype.padEnd()String.prototype.padStart()String.prototype.quote()String.prototype.repeat()String.prototype.replace()String.prototype.search()String.prototype.slice()String.prototype.small()String.prototype.split()String.prototype.startsWith()String.prototype.strike()String.prototype.sub()String.prototype.substr()String.prototype.substring()String.prototype.sup()String.prototype.toLocaleLowerCase()String.prototype.toLocaleUpperCase()String.prototype.toLowerCase()String.prototype.toSource()String.prototype.toString()String.prototype.toUpperCase()String.prototype.trim()String.prototype.trimLeft()String.prototype.trimRight()String.prototype.valueOf()String.prototype[@@iterator]()String.raw()FunctionObjectObject.prototype.__defineGetter__()Object.prototype.__defineSetter__()Object.prototype.__lookupGetter__()Object.prototype.__lookupSetter__()Object.prototype.hasOwnProperty()Object.prototype.isPrototypeOf()Object.prototype.propertyIsEnumerable()Object.prototype.toLocaleString()Object.prototype.toSource()Object.prototype.toString()Object.prototype.unwatch()Object.prototype.valueOf()Object.prototype.watch()Object.setPrototypeOf()