Javascript Regex replace string with parameter

Question

I have a string like this:

Please enter {0}, or {1} and {0}, maybe we have {2} or event {3}.

Of course I have an array hold the value with corresponding index like:

const values = ['zero', 'one', 'two', 'three']

I try to replace all the pattern {number} with many ways, the code below is one of them but it still haven't work:

for (let i = 0; i < values.length; i++) {
    const regex = new RegExp(`\\b{${i}}\\b`, 'g')
    message.replaceAll(regex, values[i])
  }

Expected result:

Please enter zero, or one and zero, maybe we have two or event three.

Javascript strings are immutable. Calling replaceAll without assignment is useless. — ASDFGerte
– ASDFGerte, Commented Jun 14, 2021 at 17:37
@ASDFGerte But this is not the only problem why this does not work. — The fourth bird
– The fourth bird, Commented Jun 14, 2021 at 17:55

The fourth bird · Accepted Answer · 2021-06-14 17:55:06Z

4

Creating a regex using const regex = new RegExp(\\b{${i}}\\b, 'g') will generate a regex like /\b{0}\b/ and is not a valid expression.

Also, you are not overwriting the value of message, and you do not need a new RegExp to do the replacements.

You can use the counter between the curly braces to get the string to replace using {${i}}

let message = "Please enter {0}, or {1} and {0}, maybe we have {2} or event {3}.";
const values = ['zero', 'one', 'two', 'three']
for (let i = 0; i < values.length; i++) {
  message = message.replaceAll(`{${i}}`, values[i])
}
console.log(message);

edited Jun 14, 2021 at 17:55

answered Jun 14, 2021 at 17:38

The fourth bird

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1 Comment

thep nguyen nhu Over a year ago

Awesome, It's work. I used to try this but forget to re assign message!!! Thank you.

MonkeyZeus · Accepted Answer · 2021-06-14 18:15:32Z

2

You need to make use of .replace()'s anonymous callback.

// The text
var message = `Please enter {0}, or {1} and {0}, maybe we have {2} or {6} event {3}.`;

// Our replacements, make them global with var
var values = ['zero', 'one', 'two', 'three'];

// Capture desired content and save the digits into its own capture group
console.log( message.replace( /\{(\d+)\}/g, function(matches, dollar_one){
  
  // If we have a replacement then return it
  if(values[dollar_one]){
    return values[dollar_one];
  }
  // Otherwise return the whole match. {6} from the example above
  else{
    return matches;
  }
}));

Output

Please enter zero, or one and zero, maybe we have two or {6} event three.

edited Jun 14, 2021 at 18:15

answered Jun 14, 2021 at 17:39

MonkeyZeus

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3 Comments

thep nguyen nhu Over a year ago

thank for your help. The fourth bird's way is what I need and simple for me :)

MonkeyZeus Over a year ago

@thepnguyennhu No problem. The advantage of my answer is that it has recursion mitigation. Try values = ['zero', '{3}', 'two', 'three']; with mine and with theirs to see what I mean.

thep nguyen nhu Over a year ago

yep, to make sure is existed in values

anubhava · Accepted Answer · 2021-06-14 18:26:17Z

1

Similar to @MonkeyZeus here is another way to use anonymous replacer in .replace(/re/, replacer):

const message = `Please enter {0}, or {1} and {0}, maybe we have {2} then event {6}/{5} and {3}.`;

// Our replacements
var values = ['zero', 'one', 'two', 'three'];

// match {digits} and replace with values[index]
var r = message.replace(/{(\d+)}/g, (m, g1) => 
        g1 in values ? values[g1] : m);

console.log(r);
//=> Please enter zero, or one and zero, maybe we have two then event {6}/{5} and three.

answered Jun 14, 2021 at 18:26

anubhava

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