截取abcdefg右边的fg
方法一
<script>
string="abcdefg"
alert(string.substring(string.length-2,string.length))
</script>
方法2
<script>
alert("abcdefg".match(/.*(.{2})/)[1])
</script>
<script>
alert("abcdefg".match(/.{2}$/))
</script>
方法3
<script>
alert("abcdefg".slice(-2)) //推荐这个，比较简单,-2表示取右边两个字符
</script>