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I am trying to replace values in a string with the parable jSON property in an object.

var value = "/sessions/:sessionId/events/:id";
var result = replace(value, { sessionId : 1 , id : 23 });

// result : "/sessions/1/events/23"
console.log(result);

Is it possible with JavaScript (I'm sure it is)? Not sure about the most efficient way to do this and how to handle it when all the values inside the template string are not matched.

Thanks in advance.

Update (Solution)

var url = function (template, parameters) {

    var extra = [];

    for (param in parameters) {
        if (value.indexOf(param) < 0) {
            extra.push(param + '=' + parameters[param]);
        }
    }

    var result = template.replace(/:(\w+)/g, function (substring, match) {
        var routeValue = parameters[match];
        if (!routeValue) {
            throw "missing route value for " + match + ' in "' + template +'"';
        }
        return routeValue;
    });

    if (result.indexOf("/:") > 0) {
        throw "not all route values were matched";
    }

    return (extra.length === 0) ? result : result + "?" + extra.join("&");
};

var value = "/sessions/:sessionId/events/:id";
var data = {
    sessionId: 1,
    id: 23,
    term: "butter"
};

// result : /sessions/1/events/21?term=butter
console.log(url(value, data));

I am trying to replace values in a string with the parable jSON property in an object.

var value = "/sessions/:sessionId/events/:id";
var result = replace(value, { sessionId : 1 , id : 23 });

// result : "/sessions/1/events/23"
console.log(result);

Is it possible with JavaScript (I'm sure it is)? Not sure about the most efficient way to do this and how to handle it when all the values inside the template string are not matched.

Thanks in advance.

Update (Solution)

var url = function (template, parameters) {

    var extra = [];

    for (param in parameters) {
        if (value.indexOf(param) < 0) {
            extra.push(param + '=' + parameters[param]);
        }
    }

    var result = template.replace(/:(\w+)/g, function (substring, match) {
        var routeValue = parameters[match];
        if (!routeValue) {
            throw "missing route value for " + match + ' in "' + template +'"';
        }
        return routeValue;
    });

    if (result.indexOf("/:") > 0) {
        throw "not all route values were matched";
    }

    return (extra.length === 0) ? result : result + "?" + extra.join("&");
};

var value = "/sessions/:sessionId/events/:id";
var data = {
    sessionId: 1,
    id: 23,
    term: "butter"
};

// result : /sessions/1/events/21?term=butter
console.log(url(value, data));

• javascript
• regex
• string

Share Improve this question Follow edited Jul 24, 2013 at 17:35 Khalid Abuhakmeh asked Jul 24, 2013 at 15:24 Khalid AbuhakmehKhalid Abuhakmeh 10.8k1010 gold badges5454 silver badges7575 bronze badges 2

• 2 That's not JSON. It's a JavaScript object. JSON is a string representation of data that just so happens to very closely resemble JavaScript syntax. It's onlY JSON if it's a string. { sessionId : 1 , id : 23 } is an object literal, '{"sessionId": 1, "id": 23}' (a string) is JSON. – gen_Eric Commented Jul 24, 2013 at 15:36
• The template url format is similar to AngularJs $resource url template, looking at github./angular/angular.js/blob/master/src/ngResource/… setUrlParams() does the magic and also handles url encoding. – Mark Coleman Commented Jul 24, 2013 at 19:13

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3 Answers 3

Sorted by: Reset to default 6

A regex would work just fine here.

var value = "/sessions/:sessionId/events/:id";
var obj = { sessionId : 1 , id : 23 };

var result = value.replace(/:(\w+)(\/|\b)/g, function(substring, match, nextMatch){
    return obj[match] + nextMatch;
});

Assuming you have the following javascript object:

var myObject = { sessionId : 1 , id : 23 };

you can loop each property and do a replace on the original string...

var value = "/sessions/:sessionId/events/:id";

for(var item in myObject){
    value = value.replace(item, myObject[item]);
}

//value = "/sessions/:1/events/:23"

Here is a working example

It is not clear if you want to keep the : characters or not. If not, then you can just include that in your replace function:

value = value.replace(':' + item, myObject[item]);

---

Checking for missing parameters

If you have any extra values in your object that do not exist in your input string, then they will not have any effect. If however, you want to take action if one of the items is not found in the original string, then you can do a check in the loop:

var noMatch = false;
for(var item in myObject){
    if(value.indexOf(item) < 0){
        noMatch = true;
    }
    value = value.replace(item, myObject[item]);
}
if(noMatch){
    //something is wrong!
}

---

Dealing with JSON

If you do actually have a JSON string to begin with, you can convert that to an object with the following:

var jsonString = '{"sessionId": 1, "id": 23}';
var myObject = JSON.parse(jsonString);

here is another way of doing it.

http://jsfiddle/rayweb_on/suHej/

 var value = "/sessions/:sessionId/events/:id";
 var source = { sessionId : 1 , id : 23 };
 var result = value.replace(":sessionId",source.sessionId);
 var result = result.replace(":id",source.id);
 console.log(result);

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