Replacing parts of a String using RegEx - Javascript

Question

I am trying to replace the 'parameters' in my string with the actual values of the parameters using the replace() method, but for some reason I cannot get it it to work. The string I am using is:

var temp = "This {{application}} will be down from {{start}} to {{finish}}."

I want to replace {{application}} with the application name, and so on.

var regEx = /{{(.*?)}}/;

This is the regex I use to grab the values between the brackets and that part works. Here is the rest of my code:

if (regEx.exec(temp)[1] === "application") {
     temp.replace(regEx, params.value);
}

'params.value' is the name of the application. I thought this would work, but it is not.

why not just use simple plain replace? jsfiddle.net/th6crbbm — Sharky
– Sharky, Commented Feb 2, 2016 at 13:34
you know, you are missing a semicolon at the end on your var temp =...... maybe thats why replace doesnt work. — Sharky
– Sharky, Commented Feb 2, 2016 at 13:45

Tushar · Accepted Answer · 2016-02-02 13:53:25Z

To replace only a single string(static)

var appName = "application"; // String to replace
var regex = new RegExp("{{" + appName + "}}", "g"); // Use `g` flag to replace all occurrences of `{{application}}`
temp = temp.replace(regex, param.value);

var appName = "application",
    regex = new RegExp("{{" + appName + "}}", "g"),
    temp = "This {{application}} will be down from {{start}} to {{finish}}.";

var param = {
    value: 'StackOverflow'
};
temp = temp.replace(regex, param.value);

console.log(temp);
document.body.innerHTML = temp;

To replace all the strings inside brackets by their respective values(Dynamic)

You can use String#replace with an object to replace values.

var regex = /{{(.*?)}}/g;
// Match all the strings in the `{{` and `}}`
// And put the value without brackets in captured group

temp = temp.replace(regex, function(m, firstGroup) {
    // m: Complete string i.e. `{{foobar}}`
    // firstGroup: The string inside the brackets

    return params[firstGroup] || 'Value not found in params';
    // If the value for the key exists in the `params` object
    //     replace the string by that value
    // else
    //     replace by some default string
});

var params = {
    application: 'Stack Overflow',
    start: 'On Sunrise',
    finish: 'In Dreams'
};

var temp = "This {{application}} will be down from {{start}} to {{finish}}.";

var regex = /{{(.*?)}}/g;
temp = temp.replace(regex, function(m, firstGroup) {
    return params[firstGroup] || 'Value not found in params';
});

console.log(temp);
document.body.innerHTML = temp;

Cyrbil · Accepted Answer · 2016-02-03 10:23:50Z

1

Here is an helper function to produce what you expect

function replace(str, dict) {
    return str.replace(/{{(.*?)}}/g, function(match, $1) {
        return dict[$1] || match;
    });
}

replace(
    "This {{application}} will be down from {{start}} to {{finish}}.",
    {
        'application': 'pigeon',
        'start': '8am',
        'finish': '9pm'
    }
);
// "This pigeon will be down from 8am to 9pm."

This will accept a mapping of values to replace and the replacement. And returns the string correctly formatted.

edited Feb 3, 2016 at 10:23

answered Feb 2, 2016 at 13:42

Cyrbil

6,5081 gold badge27 silver badges42 bronze badges

2 Comments

user663031 Over a year ago

This will only replace the first occurrence of each marker.

Cyrbil Over a year ago

You are right ! So yeah ... regex are mandatory (or an ugly loop) :). I edit for a regex.

Wiktor Stribiżew · Accepted Answer · 2016-02-02 13:36:36Z

0

You can use a callback inside a replace to evaluate the capture group contents:

var name = "Google";
var temp = "This {{application}} will be down from {{start}} to {{finish}}.";
var res = temp.replace(/{{(.*?)}}/g, function (m, g) {
  return g === "application" ? name : m;
});
document.body.innerHTML = res;

Here, m is the whole matched text with braces and g is the submatch without braces.

answered Feb 2, 2016 at 13:36

Wiktor Stribiżew

631k41 gold badges502 silver badges632 bronze badges

Collectives™ on Stack Overflow

Replacing parts of a String using RegEx - Javascript

3 Answers 3

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related