Javascript - The quickest and most efficient way to replace object-based values in text

Question

I have an object that looks like this:

var obj = {
    a: "text",
    b: "text 2",
    c: "text 3",
    ...
}

and I have a bunch of strings that look like this:

var stringA = "http://{{a}}.something.com/",
    stringB = "http://something.{{b}}.com/",
    stringC = "http://something.com/{{c}}";

I want to replace {{(\w)}} with it's equivalent by going through obj and checking if it has my matched value for every string, but I'm sure there is a better and faster way to do so.

Any ideas?

ipr101 · Accepted Answer · 2011-10-18 11:16:52Z

6

Douglas Crockford wrote a function called supplant that does almost exactly what you want. I've altered the function slightly to match your double curly braces -

if (typeof String.prototype.supplant !== 'function') {
    String.prototype.supplant = function (o) {
        return this.replace(/{{([^{}]*)}}/g, function (a, b) {
            var r = o[b];
            return typeof r === 'string' ? r : a;
        });
    };
}

var obj = {
    a: "text",
    b: "text 2",
    c: "text 3"
}

var stringA = "http://{{a}}.something.com/",
    stringB = "http://something.{{b}}.com/",
    stringC = "http://something.com/{{c}}";

alert(stringA.supplant(obj));

Demo - http://jsfiddle.net/saZGg/

answered Oct 18, 2011 at 11:16

ipr101

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1 Comment

Zain Shaikh Over a year ago

any way to map deep objects with dot notation?

Raynos · Accepted Answer · 2011-10-18 11:53:02Z

2

var arr = /(.*){{(\w)}}(.*)/.exec(stringA);
arr[2] = obj[arr[2]];
arr.shift(); // remove full string at start
var newString = arr.join("");

Generally run a regular expression on the string,
execute and turn it into an array.
Swap one of the groups for the value in your object hash
join the array into your "compiled" string.

Or use one of the .replace solutions which is arguebly more elegant.

edited Oct 18, 2011 at 11:53

answered Oct 18, 2011 at 11:16

Raynos

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1 Comment

pimvdb Over a year ago

.exec will return the string itself as its first argument, so you'll end up with the unaltered string prepended.

Felix Kling · Accepted Answer · 2011-10-18 11:16:51Z

1

This should do it:

function format(str, values) {
    return str.replace(/{{(\w)}}/g, function(match, name) {
        return values[name] || match;
    });
}

It just looks up whether the object has a property with the captured name. If not, nothing is replaced.

Usage:

var str = format(stringA, obj);

answered Oct 18, 2011 at 11:16

Felix Kling

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