标题: JavaScript中如何判断字符串以指定子串结尾

https://scz.617.cn/misc/201711061152.txt

写windbg jscript插件时冷不丁碰上这个需求，判断字符串以指定子串结尾。对js编
程不熟，最初自己傻乎乎地实现了一个版本，后来无意中发现有内置endsWith()。此
处列举一些实现，非指导性，仅仅是收藏代码片段。

1)

内置版本

--------------------------------------------------------------------------
if ( a.endsWith( b ) )
--------------------------------------------------------------------------

2)

我最初的2B版本，用substring()实现，而且用"=="，没用"==="

--------------------------------------------------------------------------
String.prototype.endsWith   =
function ( str )
{
    if ( str == null || str.length > this.length )
    {
        return false;
    }
    if ( this.substring( this.length - str.length ) == str )
    {
        return true;
    }
    else
    {
        return false;
    }
};

if ( a.endsWith( b ) )
--------------------------------------------------------------------------
function PrivateStringEndWith ( a, b )
{
    if ( b == null || a == null || b.length > a.length )
    {
        return false;
    }
    if ( a.substring( a.length - b.length ) == b )
    {
        return true;
    }
    else
    {
        return false;
    }
}

if ( PrivateStringEndWith( a, b ) )
--------------------------------------------------------------------------

3)

用indexOf()实现

--------------------------------------------------------------------------
String.prototype.endsWith   =
function ( str )
{
    return this.indexOf( str, this.length - str.length ) !== -1;
};
--------------------------------------------------------------------------

4)

用substr()实现

--------------------------------------------------------------------------
String.prototype.endsWith   =
function ( str )
{
    return this.substr( -str.length ) === str;
};
--------------------------------------------------------------------------

可以多一个预检查，没有内置版本时才自己实现

--------------------------------------------------------------------------
if ( typeof String.prototype.endsWith !== 'function' )
{
    String.prototype.endsWith   =
    function ( str )
    {
        return this.substr( -str.length ) === str;
    }
};
--------------------------------------------------------------------------

5)

用正则表达式实现

--------------------------------------------------------------------------
String.prototype.endsWith   =
function ( str )
{
    var reg = new RegExp( str+"$" );

    return reg.test( this );
};
--------------------------------------------------------------------------