从JavaScript字符串中切出一个字符

Question

I want to remove what is inside the last bracket of a string.

This is the ids string:

rule_Group[0][5]

This is my Javascript code

var str = 'rule_Group[0][5]';

var a = str.lastIndexOf("[") + 1;
var b = str.lastIndexOf("]") - 1;
var res = str.substr(a,b)

document.write(res)

I want to keep the 5 in the brackets. No matter what JS doesn't allow me to cut out just one character. I have even manually tried to do this with no luck.

Any advice?

Answer 1

use substring instead of substr .

var str = 'rule_Group[0][5]';

var a = str.lastIndexOf("[") + 1;
var b = str.lastIndexOf("]");
var res = str.substring(a,b)

document.write(res)

Answer 2

The second parameter of substr is the length of the substring to return, not an index. So if you know you want just one character, this would work:

var a = str.lastIndexOf("[") + 1;
var res = str.substr(a, 1);

Of if you don't know how long the substring is, use this:

var a = str.lastIndexOf("[") + 1;
var b = str.lastIndexOf("]");
var res = str.substr(a, b - a);

Answer 3

I would do it this way

var str = 'rule_Group[0][5]';
var numb = str.split('[').pop().replace(']','');

FIDDLE

Just seems easier ?

Answer 4

I think you can just do this:

var a = str.lastIndexOf("[")+1;
var res = str.charAt(a);

Try it out and let me know if it works :-)

Cheers,

Roiw

EDIT:

You can use regular expressions if you want (this will work for your case):

var str = "rule_Group[0][123456789]";
var patt1=new RegExp("^.*?\\[.*?\\[");  
var patt2=new RegExp("\\].*?$");
var result = str.replace(patt1,"");
result = result.replace(patt2,"");

Cheers,

Roiw