Javascript - 如何删除字符串开头的空格

Question

我想删除字符串开头的空格它应该只删除字符串开头的空格，其他空格应该在那里。

var string=' This is test';

Answer 1

This is what you want:

function ltrim(str) {
  if(!str) return str;
  return str.replace(/^\s+/g, '');
}

Also for ordinary trim in IE8+:

function trimStr(str) {
  if(!str) return str;
  return str.replace(/^\s+|\s+$/g, '');
}

And for trimming the right side:

function rtrim(str) {
  if(!str) return str;
  return str.replace(/\s+$/g, '');
}

Or as polyfill:

// for IE8
if (!String.prototype.trim)
{
    String.prototype.trim = function ()
    {
        // return this.replace(/^\s+|\s+$/g, '');
        return this.replace(/^[\s\uFEFF\xA0]+|[\s\uFEFF\xA0]+$/g, '');
    };
}

if (!String.prototype.trimStart)
{
    String.prototype.trimStart = function ()
    {
        // return this.replace(/^\s+/g, '');
        return this.replace(/^[\s\uFEFF\xA0]+/g, '');
    };
}

if (!String.prototype.trimEnd)
{
    String.prototype.trimEnd = function ()
    {
        // return this.replace(/\s+$/g, '');
        return this.replace(/[\s\uFEFF\xA0]+$/g, '');
    };
}

Note:
\\s: includes spaces, tabs \\t, newlines \\n and few other rare characters, such as \\v, \\f and \\r.
\: Unicode Character 'ZERO WIDTH NO-BREAK SPACE' (U+FEFF)
\\xA0: ASCII 0xA0 (160: non-breaking space) is not recognised as a space character

Answer 2

Try to use javascript's trim() function, Basically it will remove the leading and trailing spaces from a string.

var string=' This is test';
string = string.trim();

DEMO

So as per the conversation happened in the comment area, in order to attain the backward browser compatibility just use jquery's $.trim(str)

var string=' This is test';    
string = $.trim(string)

Answer 3

You can use String.prototype.trimStart(). Like this:

myString=myString.trimStart();

An if you want to trim the tail, you can use:

myString=myString.trimEnd();

Notice, this 2 functions are not supported on IE. For IE you need to use polyfills for them.

Answer 4

You should use javascript trim function

var str = "       Hello World!        ";
alert(str.trim()); 

This function can also remove white spaces from the end of the string.

Answer 5

.trimLeft() can be used for this.

const str = "   string   ";
console.log(str.trimLeft());     // => "string   "

Answer 6

Just a different and a not so efficient way to do it

 var str = " My string"; function trim() { var stringStarted = false; var newString = ""; for (var i in str) { if (!stringStarted && str[i] == " ") { continue; } else if (!stringStarted) { stringStarted = true; } newString += str[i]; } return newString; } console.log(trim(str));

I am really sure this doesn't work for anything else and is not the most optimum solution, but this just popped into my mind

Answer 7

Easiest solution: (ES10 feature trimStart())

var string= 'This is a test';
console.log(string.trimStart());

Answer 8

var string=' This is test';    
$.trim(string);

Answer 9

You want to remove the space (ie whitespace) at the beginning of the string. So, could not use standard jquesy .trim() . You can use the regex to find and replace the whitespace at the beginning of the string.

Try this:

.replace(/^\s+/g, "")

Read this post

Try this:

var string='    This is test   ';
alert(string.replace(/^\s+/g, ""));

Working Example

OR if you want to remove the whitespace from the beginning and end then use .trim()