如何在Javascript中更改字符串中的特定字符

Question

I have this string in an input variable like this: var input = "javascript";

i want to change this string to "j4v4sr1pt" by replacing a with 4 and i with 1.

i tried to do something like this but didn't work for me , i am new to JavaScript .can someone tell me what i am doing wrong here ? THanks for down votes in advance :D

<script>
var input = "javascript";
var output= "";

for ( var i=0;i<input.length ; i++)
   { if ( input[i] == "a")
       {output[i] = "4"; }
     else if ( input[i] == "i")
     {  output[i] ="1"; }
     else
       output[i]=input[i];
    }// end forloop
</script>

Answer 1

In JavaScript, strings are immutable, meaning that they cannot be changed in place. Even though you can read each character of a string, you cannot write to it.

You can solve the problem with a regular expression replace:

output = input.replace(/a/g, '4').replace(/i/g, '1');

Or you can solve it by changing output from a string to an array, and then joining it to make it a string:

 var input = "javascript"; var output = []; //change this for (var i = 0; i < input.length; i++) { if (input[i] == "a") { output[i] = "4"; } else if (input[i] == "i") { output[i] = "1"; } else output[i] = input[i]; } // end forloop output= output.join(''); //change array to string console.log(output); 

Answer 2

Try the .replace() method like following:

<script>
    var input = "javascript";
    var output = input.replace("a", "4", "g").replace("i", "1", "g");
</script>

Edit : Added g flag to the replace method to replace all matches and not just the first one.