How can I perform a str_replace in JavaScript, replacing text in JavaScript?

I want to use str_replace or its similar alternative to replace some text in JavaScript.

str_replace

var text = "this is some sample text that i want to replace";
var new_text = replace_in_javascript("want", "dont want", text);
document.write("new_text");


should give

this is some sample text that i dont want to replace


If you are going to regex, what are the performance implications in
comparison to the built in replacement methods.

str_replace

20 Answers
20

Using regex for string replacement is significantly slower than using a string replace.
As demonstrated on JSPerf, you can have different levels of efficiency for creating a regex, but all of them are significantly slower than a simple string replace. The regex is slower because:

Fixed-string matches don't have backtracking, compilation steps, ranges, character classes, or a host of other features that slow down the regular expression engine. There are certainly ways to optimize regex matches, but I think it's unlikely to beat indexing into a string in the common case.

For a simple test run on the JS perf page, I've documented some of the results:


// Setup
var startString = "xxxxxxxxxabcxxxxxxabcxx";
var endStringRegEx = undefined;
var endStringString = undefined;
var endStringRegExNewStr = undefined;
var endStringRegExNew = undefined;
var endStringStoredRegEx = undefined;
var re = new RegExp("abc", "g");



// Tests
endStringRegEx = startString.replace(/abc/g, "def") // Regex
endStringString = startString.replace("abc", "def", "g") // String
endStringRegExNewStr = startString.replace(new RegExp("abc", "g"), "def"); // New Regex String
endStringRegExNew = startString.replace(new RegExp(/abc/g), "def"); // New Regexp
endStringStoredRegEx = startString.replace(re, "def") // saved regex


The results for Chrome 68 are as follows:

String replace: 9,936,093 operations/sec
Saved regex: 5,725,506 operations/sec
Regex: 5,529,504 operations/sec
New Regex String: 3,571,180 operations/sec
New Regex: 3,224,919 operations/sec


From the sake of completeness of this answer (borrowing from the comments), it's worth mentioning that .replace only replaces the first instance of the matched character. Its only possible to replace all instances with //g. The performance trade off and code elegance could be argued to be worse if replacing multiple instances name.replace(' ', '_').replace(' ', '_').replace(' ', '_'); or worse while (name.includes(' ')) { name = name.replace(' ', '_') }

.replace

//g

name.replace(' ', '_').replace(' ', '_').replace(' ', '_');

while (name.includes(' ')) { name = name.replace(' ', '_') }

.replace

//g

name.replace(' ', '_').replace(' ', '_').replace(' ', '_');

while (name.includes(' ')) { name = name.replace(' ', '_') }

You would use the replace method:

replace

text = text.replace('old', 'new');


The first argument is what you're looking for, obviously. It can also accept regular expressions.

Just remember that it does not change the original string. It only returns the new value.

More simply:

city_name=city_name.replace(/ /gi,'_');


Replaces all spaces with '_'!

.replace(/x3B/g,';')

All these methods don't modify original value, returns new strings.

var city_name = 'Some text with spaces';


Replaces 1st space with _

city_name.replace(' ', '_'); // Returns: Some_text with spaces


Replaces all spaces with _ using regex. If you need to use regex, then i recommend testing it with https://regex101.com/

city_name.replace(/ /gi,'_'); // Returns: Some_text_with_spaces


Replaces all spaces with _ without regex. Functional way.

city_name.split(' ').join('_'); // Returns: Some_text_with_spaces


You should write something like that :

var text = "this is some sample text that i want to replace";
var new_text = text.replace("want", "dont want");
document.write(new_text);


The code that others are giving you only replace one occurrence, while using regular expressions replaces them all (like @sorgit said). To replace all the "want" with "not want", us this code:

var text = "this is some sample text that i want to replace";
var new_text = text.replace(/want/g, "dont want");
document.write(new_text);


The variable "new_text" will result in being "this is some sample text that i dont want to replace".

To get a quick guide to regular expressions, go here:
http://www.cheatography.com/davechild/cheat-sheets/regular-expressions/
To learn more about str.replace(), go here:
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/String/replace
Good luck!

str.replace()

that function replaces only one occurrence.. if you need to replace
multiple occurrences you should try this function:
http://phpjs.org/functions/str_replace:527

Not necessarily.
see the Hans Kesting answer:

city_name = city_name.replace(/ /gi,'_');


hm.. Did you check replace() ?

Your code will look like this

var text = "this is some sample text that i want to replace";
var new_text = text.replace("want", "dont want");
document.write(new_text);


var new_text = text.replace("want", "dont want");


In JavaScript, you call the replace method on the String object, e.g. "this is some sample text that i want to replace".replace("want", "dont want"), which will return the replaced string.

replace

"this is some sample text that i want to replace".replace("want", "dont want")

var text = "this is some sample text that i want to replace";
var new_text = text.replace("want", "dont want"); // new_text now stores the replaced string, leaving the original untouched


JavaScript has replace() method of String object for replacing substrings. This method can have two arguments. The first argument can be a string or a regular expression pattern (regExp object) and the second argument can be a string or a function. An example of replace() method having both string arguments is shown below.

replace()

replace()

var text = 'one, two, three, one, five, one';
var new_text = text.replace('one', 'ten');
console.log(new_text) //ten, two, three, one, five, one


Note that if the first argument is the string, only the first occurrence of the substring is replaced as in the example above. To replace all occurrences of the substring you need to provide a regular expression with a g (global) flag. If you do not provide the global flag, only the first occurrence of the substring will be replaced even if you provide the regular expression as the first argument. So let's replace all occurrences of one in the above example.

g

one

var text = 'one, two, three, one, five, one';
var new_text = text.replace(/one/g, 'ten');
console.log(new_text) //ten, two, three, ten, five, ten


Note that you do not wrap the regular expression pattern in quotes which will make it a string not a regExp object. To do a case insensitive replacement you need to provide additional flag i which makes the pattern case-insensitive. In that case the above regular expression will be /one/gi. Notice the i flag added here.

i

/one/gi

i

If the second argument has a function and if there is a match the function is passed with three arguments. The arguments the function gets are the match, position of the match and the original text. You need to return what that match should be replaced with. For example,

var text = 'one, two, three, one, five, one';
var new_text = text.replace(/one/g, function(match, pos, text){
return 'ten';
});
console.log(new_text) //ten, two, three, ten, five, ten


You can have more control over the replacement text using a function as the second argument.

There are already multiple answers using str.replace() (which is fair enough for this question) and regex but you can use combination of str.split() and join() together which is faster than str.replace() and regex.

regex

str.replace()

regex

Below is working example:

var text = "this is some sample text that i want to replace";

console.log(text.split("want").join("dont want"));

If you really want a equivalent to PHP's str_replace you can use Locutus. PHP's version of str_replace support more option then what the JavaScript String.prototype.replace supports.
For example tags:

str_replace

str_replace

String.prototype.replace

//PHP
$bodytag = str_replace("%body%", "black", "<body text='%body%'>");


//JS with Locutus
var $bodytag = str_replace(['{body}', 'black', '<body text='{body}'>')


or array's

//PHP
$vowels = array("a", "e", "i", "o", "u", "A", "E", "I", "O", "U");
$onlyconsonants = str_replace($vowels, "", "Hello World of PHP");


//JS with Locutus
var $vowels = ["a", "e", "i", "o", "u", "A", "E", "I", "O", "U"];
var $onlyconsonants = str_replace($vowels, "", "Hello World of PHP");


Also this doesn't use regex instead it uses for loops. If you not want to use regex but want simple string replace you can use something like this ( based on Locutus )

function str_replace (search, replace, subject) {

var i = 0
var j = 0
var temp = ''
var repl = ''
var sl = 0
var fl = 0
var f = .concat(search)
var r = .concat(replace)
var s = subject
s = .concat(s)

for (i = 0, sl = s.length; i < sl; i++) {
if (s[i] === '') {
continue
}
for (j = 0, fl = f.length; j < fl; j++) {
temp = s[i] + ''
repl = r[0]
s[i] = (temp).split(f[j]).join(repl)
if (typeof countObj !== 'undefined') {
countObj.value += ((temp.split(f[j])).length - 1)
}
}
}
return s[0]
}
var text = "this is some sample text that i want to replace";

var new_text = str_replace ("want", "dont want", text)
document.write(new_text)

for more info see the source code https://github.com/kvz/locutus/blob/master/src/php/strings/str_replace.js

You have the following options:

var text = "this is some sample text that i want to replace and this i WANT to replace as well.";
var new_text = text.replace('want', 'dont want');
// new_text is "this is some sample text that i dont want to replace and this i WANT to replace as well"
console.log(new_text)

var text = "this is some sample text that i want to replace and this i WANT to replace as well.";
var new_text = text.replace(/want/g, 'dont want');
// new_text is "this is some sample text that i dont want to replace and this i WANT to replace as well
console.log(new_text)

var text = "this is some sample text that i want to replace and this i WANT to replace as well.";
var new_text = text.replace(/want/gi, 'dont want');
// new_text is "this is some sample text that i dont want to replace and this i dont want to replace as well
console.log(new_text)

More info -> here

In Javascript, replace function available to replace sub-string from given string with new one.
Use:

var text = "this is some sample text that i want to replace";
var new_text = text.replace("want", "dont want");
console.log(new_text);


You can even use regular expression with this function. For example, if want to replace all occurrences of , with ..

,

.

var text = "123,123,123";
var new_text = text.replace(/,/g, ".");
console.log(new_text);


Here g modifier used to match globally all available matches.

g

Method to replace substring in a sentence using React:

replace substring in a sentence

const replace_in_javascript = (oldSubStr, newSubStr, sentence) => {
let newStr = "";
let i = 0;
sentence.split(" ").forEach(obj => {
if (obj.toUpperCase() === oldSubStr.toUpperCase()) {
newStr = i === 0 ? newSubStr : newStr + " " + newSubStr;
i = i + 1;
} else {
newStr = i === 0 ? obj : newStr + " " + obj;
i = i + 1;
}
});
return newStr;
};


RunMethodHere

If you don't want to use regex then you can use this function which will replace all in a string

function ReplaceAll(mystring, search_word, replace_with)
{
while (mystring.includes(search_word))
{
mystring = mystring.replace(search_word, replace_with);
}

return mystring;
}


var mystring = ReplaceAll("Test Test", "Test", "Hello");


You can use

text.replace('old', 'new')


And to change multiple values in one string at once, for example to change # to string v and _ to string w:

text.replace(/#|_/g,function(match) {return (match=="#")? v: w;});


Use JS String.prototype.replace first argument should be Regex pattern or String and Second argument should be a String or function.

String.prototype.replace

str.replace(regexp|substr, newSubStr|function);

str.replace(regexp|substr, newSubStr|function);

Ex:

var str = 'this is some sample text that i want to replace';
var newstr = str.replace(/want/i, "dont't want");
document.write(newstr); // this is some sample text that i don't want to replace

var str = 'this is some sample text that i want to replace';
var newstr = str.replace(/want/i, "dont't want");
document.write(newstr); // this is some sample text that i don't want to replace

Added a method replace_in_javascript which will satisfy your requirement. Also found that you are writing a string "new_text" in document.write() which is supposed to refer to a variable new_text.

replace_in_javascript

"new_text"

document.write()

new_text

let replace_in_javascript= (replaceble, replaceTo, text) => {
return text.replace(replaceble, replaceTo)
}

var text = "this is some sample text that i want to replace";
var new_text = replace_in_javascript("want", "dont want", text);
document.write(new_text);

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