Replacing %1 and %2 in my javascript string

Question

Lets say I have the following string in my javascript code:

var myText = 'Hello %1. How are you %2?';

Now I would like to inject something in place of %1 and %2 in the above string. I can do:

var result = myText.replace('%1', 'John').replace('%2', 'today');

I wonder if there is a better way of doing than calling 2 times the replace function.

Thanks.

This problem is discussed here: http://stackoverflow.com/questions/610406/javascript-equivalent-to-printf-string-format — Ahmed Masud, May 04 '13 at 07:46

elclanrs · Accepted Answer · 2013-05-04T07:53:13.487

18

How about a little format helper? That's basically what you need:

function format(str, arr) {
  return str.replace(/%(\d+)/g, function(_,m) {
    return arr[--m];
  });
}

var myText = 'Hello %1. How are you %2?';
var values = ['John','today'];

var result = format(myText, values);

console.log(result); //=> "Hello John. How are you today?"

Demo: http://jsbin.com/uzowuw/1/edit

edited May 04 '13 at 07:53

answered May 04 '13 at 07:45

elclanrs

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171

Your approach should allow for %1 to be included using an escape %; for example %%1 ... It may also be useful to allow hashes like %{name} really do have a look at the sprintf here to see a proper implementation that will cover any future permutations http://www.diveintojavascript.com/projects/javascript-sprintf – Ahmed Masud May 04 '13 at 07:51
Add a fiddle! This looks great :) – Ian May 04 '13 at 07:51
1

Added fiddle. @AhmedMasud: I usually just do `{1}` with a slightly different regex. It works for all my needs. But yes, there are libraries for more robust solutions. – elclanrs May 04 '13 at 07:54
@AhmedMasud Although that library is great, the OP really didnt ask for all that. This answer isnt perfect (in the sense that it doesnt have everything you described, nor does it have everything sprintf does), but its a great solution as is. – Ian May 04 '13 at 07:54
Thank you all, very instructive. – Bronzato May 04 '13 at 07:59
Try this one if you don't want the array: http://codepen.io/anon/pen/gautE – Eric Elliott Oct 17 '13 at 12:21

score 0 · Answer 2 · answered May 04 '13 at 07:54

0

Try this sample

function setCharAt(str,chr,rep) {
    var index = -1;
    index= str.indexOf(chr);
    var len= chr.length;
    if(index > str.length-1) return str;
    return str.substr(0,index) + rep + str.substr(index+len);
}

var myText = 'Hello %1. How are you %2?';

var result = setCharAt(myText,"%1","John");
var result = setCharAt(result,"%2","today");

alert(result);

answered May 04 '13 at 07:54

Akshay Joy

1,765
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DEMO http://jsfiddle.net/6JUYD/ – Akshay Joy May 04 '13 at 07:55

score 0 · Answer 3 · answered May 04 '13 at 08:06

This is meant just as a complex comment to elclarns' great answer, suggesting these alternatives:

Can be written as String.prototype
Can use arguments

The function can be altered to

String.prototype.format = function() {
  var args=arguments;
  return this.replace(/%(\d+)/g, function(_,m) {
    return args[--m];
  });
}

And called this way

var result = "I am %1, %2 years old %1".format("Jan",32);
// I am Jan, 32 years old Jan

Replacing %1 and %2 in my javascript string

3 Answers3

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