如何使用jQuery的trim（）函数

Question

As discussed in many questions on stack - IE 8 wont accept .trim() , but the jQuery framework takes care of that.

I don't know how to translate my function to use that version of trim (I thought I was already using jQuery), could someone advise? Here is my code:

$('input').val(function(index, val){
    return val.replace('Please Select', '').trim();
});

This is designed to replace the string with nothing.

I've tried:

$('input').val(function(index, val){
    return val.replace('Please Select', '')$.trim();
});

but that was no good.

Answer 1

$.trim(val.replace('Please Select', ''))

http://api.jquery.com/jQuery.trim/

Answer 2

IE8 doesn't have a native trim method, generally, I just augment the prototype:

if (!String.prototype.trim)
{
    String.prototype.trim = function()
    {
        return this.replace(/^\s+|\s+$/g,'');
    };
}

This is the shortest regex to trim a string, but I have heard it say that .replace(/^\\s\\s*/,'').replace(/\\s*\\s$/,'') is (marginally) faster... the choice is yours

If you really want to use jQuery for this, of course, you'll have to make the target string the context of the called method ( $.trim calls the method on $ === the jQuery object), so make the String a jQ object:

$('  foo bar  ').trim();//returns "foo bar"
//compared to augmented prototype:
'   foo bar  '.trim();//returns "foo bar"

The benefit of an augmented prototype is that you don't have the additional overhead of creating a new jQuery object, whereas using the prototype-approach relies on JS to wrap the string in a native String object and apply the method to that. Basically, it's the same operation, but it should be a marginally more efficient, because jQuery does a bunch of checks to any string passed to the jQuery constructor ( $() )

Answer 3

Try this:

$.trim(val.replace('Please Select', ''));

Here's the Trim() entry in the documentation.