2.9: Regular Expressions: replace() – Programming with Text


In this video, I cover the JavaScript function replace(). The function allows you to search for a string (by matching a regular expression) and replace that string. The replacement can be a literal string itself or you can pass in a callback where you can use logic and programming to generate a replacement string based on anything you can imagine.

This is the ninth video in a series on Regular Expressions, which is part of the “Programming from A to Z” course at ITP (

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MDN’s Regular Expressions Reference:
Regular Expressions on Wikipedia:
Book Mastering Regular Expressions:
ITP from Tisch School of the Arts:

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  1. Guy, you're my favorite programmer youtuber.

    Thanks for helping me in this session so goodly.
    Greetings from Brazil 😀

  2. Those who have finished this guy's amazing Regular Expressions tutorial,
    Here is a good coding practice related to Regular Expressions from codewars!

    It's always good to try to implement skills you just learned and try to use them in order to solve something!
    Keep it up guys~

  3. I used regex to seperate out half moves in chess to different capture groups from PGN files, to create a PGN viewer ( a chess game replayer) in JS 🙂 I love regex now, it saved me so much headache 😀

  4. Write down Regular Expressions that can extract Strings 123.jpg and 432.png from

    String axhdsjk123.jpg.jpg and hjhsd432.png.png

    How to?

  5. Here's a useful way to get a Date object easily using RegExp.

    function getDate (str) {
    const matcher = /d{1,2}-d{1,2}-d{4}/;
    const match = matcher.exec(str);
    return new Date(match[3], match[2], match[1]);

  6. Very usefull, now I finally can say that I've learned about RegEx whit your tutorials series. Thank you very much teacher Danniel, regards from Mexico :-). YOU ARE THE BEST!!!

  7. This video just triggered a Eureka moment in my brain. I'm 35 and just started learning coding 4 months ago and I think I've just turned a corner. Thank u man. I'm not sure what u did, but it's like a fog has just lifted off of javascript for me.

  8. very useful tutorials….I've spent 4 hours trying to solve a problem, after watching your video I solved it within 2 minutes !!!

  9. function imprim(){
    var t5= ''
    ctx.font = "Arial 14px"
    positionY= 50
    while( count< canvas.height/2){

    positionY= positionY + 10
    count = count +1}
    function replace(t1){
    var t5 = t1.replace(/t1/g,"php")

    var t1= ' Hello javascript'
    var t2= t1[3]
    var t3 = t1.length
    help me please

  10. is it possible to say I want regex to capture a,b and c, but replace a with a certain section of a, replace be with a certian section of b, and replace c with a certain section of c… I was thinking that | would be used in the match part of the replace , but I havent found a decent example

  11. that was an amazing tutorial, i didn't even noticed that i'm watching the last one.
    in few hours i watched all your videos and i'm so thankful to learn from you.
    greetings from Syria
    you are the best.


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