Replace keys in string by value based on key–value entries in object

Question

I’m trying to convert each integer in a string to its corresponding value in an object based on its key–value entries. For example if I have:

var arr = {
    "3": "value_three",
    "6": "value_six",
    "234": "other_value"
  };
var str = "I want value 3 here and value 234 here";

I would expext the output to be:

new_str = "I want value_three here and value other_value here"

Answer 1

I'm just doing this off the top of my head, but this should work.

var new_str = str;

for (var key in arr) {
    if (!arr.hasOwnProperty(key)) {
        continue;
    }

    new_str = new_str.replace(key, arr[key]);
}

If you wanted all occurrences of the number to be replaced, you'd need to incorporate a Regex into the mix:

var new_str = str;

for (var key in arr) {
    if (!arr.hasOwnProperty(key)) {
        continue;
    }

    new_str = new_str.replace(new RegExp(key, "g"), arr[key]);
}

Also, I'd pick another name other than arr, as that implies it's an array when it's clearly an object. Also, make sure you only use for-in loops on objects, not arrays, because of issues with prototype leakage and others.

You can also do this with jQuery, but it's probably overkill:

var new_str = str;

$.each(arr, function (key, value) {
    new_str = new_str.replace(key, value);
});

Answer 2

Suppose you have an object like arr, with str defined and new_str declared. Then, assuming that we aim for a general solution the following works:

var arr = { "3": "value_three", "6": "value_six", "234": "other_value" };
var str = "I want value 3 here and value 234 here";

// Building a regex like `/3|6|234/g`
let re = new RegExp(Object.keys(arr).join('|'), 'g');

// Arrow function is approximately equivalent to
// an anonymous function like `function(match) { return arr[match]; }`
new_str = str.replace(re, match => arr[match]);

console.log(new_str);

Just as a little side note, arr given your example is an Object. (I realize that they are sometimes called associative arrays as well; just pointing it out).