CODEWITHSUNDEEP
javascriptregexstring
Miha Šušteršič
Miha Šušteršič

Reputation: 10052

Replacing multiple characters in a string with a string rewrites characters

I have a variable (in this example var str = "I!%1$s-I!%2$s TTL!%3$s";), in which I want to replace the % with elements from an array (var regex = ['aaa', 'bbb', 'ccc'];).

I google around a bit and found this solution, but I'm having trouble implementing it. My problem is that I want to replace a single character with multiple characters, and then continue the string, but this just overwrites the characters. I actually have no idea why.

Any help is appreciated, my code below

String.prototype.replaceAt = function(index, character) {
  return this.substr(0, index) + character + this.substr(index + character.length);
}

var str = "I!%1$s-I!%2$s TTL!%3$s";
var regex = ['replace', 'replace', 'replace'];

//find position of %
var find = /%/gi,
  result, pos = [];
while ((result = find.exec(str))) {
  pos.push(result.index);
}

//replace % with regex elements
for (x = 0; x < pos.length; x++) {
  str = str.replaceAt(pos[x], regex[x]);
}

document.write(str);

Upvotes: 3

Views: 170

Answers (1)

thefourtheye
thefourtheye

Reputation: 239483

Use replacement function, like this

var str = "I!%1$s-I!%2$s TTL!%3$s";
var regex = ['[123]', '[456]', '[789]'];

console.log(str.replace(/%(\d+)/g, function(match, group1) {
  return regex[parseInt(group1) - 1] + group1;
}));
// I![123]1$s-I![456]2$s TTL![789]3$s

The RegEx /%(\d+)/g matches anything of the pattern % followed by one or more digits. And it captures the digits as a group. Then the exact match and the group is passed to the function to get the actual replacement. In the function, you convert the group to a number with parseInt and return the respective value from the regex array.

Upvotes: 3

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