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I'd like to do the following

var obj = {
  animal: "${animal}"
};

var res = magic(obj, {animal: "cat"});

// res => {animal: "cat"}

magic is some function that does the dirty work. Obviously obj could be more plex with multiple keys, nested arrays and so on. The template variable could be inside an array like this

var obj = {
  animals: ["cat", "dog", "${animal}", "cow"]
};

and it could be anywhere in the array so simply doing obj.animals[2] = "bat"; isn't feasible.

I've found the underscore-tpl library with which I can achieve what I want, but I would like to know if there are other solutions for future reference and because I had a hard time finding underscore-tpl in the first place.

My actual use is case is that I have a config.json file where I have several declarations like the following

{
  "task1": {
    "mand": "mand-line-program",
    "args": [
      "--input", "{{input}}",
      "--flag1",
      "--output", "{{output}}",
      "--flag2",
    ],
    "options": {
      "cwd": "path-to-working-dir"
    }
  }
}

I parse this consig.json using JSON.parse(...) and I call require("child_process").spawn with the mand, args and options parameters declared in the file, however args change a lot, flags added, reordered and stuff, so simply doing config.task1.args[1] = "<input value>"; involves changing the code that invokes spawn and this is as error prone as it gets.

Update

Based on the accepted answer I've created a simple package (located here) which I can include in my projects, feel free to use it.

I'd like to do the following

var obj = {
  animal: "${animal}"
};

var res = magic(obj, {animal: "cat"});

// res => {animal: "cat"}

magic is some function that does the dirty work. Obviously obj could be more plex with multiple keys, nested arrays and so on. The template variable could be inside an array like this

var obj = {
  animals: ["cat", "dog", "${animal}", "cow"]
};

and it could be anywhere in the array so simply doing obj.animals[2] = "bat"; isn't feasible.

I've found the underscore-tpl library with which I can achieve what I want, but I would like to know if there are other solutions for future reference and because I had a hard time finding underscore-tpl in the first place.

My actual use is case is that I have a config.json file where I have several declarations like the following

{
  "task1": {
    "mand": "mand-line-program",
    "args": [
      "--input", "{{input}}",
      "--flag1",
      "--output", "{{output}}",
      "--flag2",
    ],
    "options": {
      "cwd": "path-to-working-dir"
    }
  }
}

I parse this consig.json using JSON.parse(...) and I call require("child_process").spawn with the mand, args and options parameters declared in the file, however args change a lot, flags added, reordered and stuff, so simply doing config.task1.args[1] = "<input value>"; involves changing the code that invokes spawn and this is as error prone as it gets.

Update

Based on the accepted answer I've created a simple package (located here) which I can include in my projects, feel free to use it.

• javascript
• json
• string-interpolation
• underscore.js-templating

Share Improve this question Follow edited May 23, 2017 at 10:29 CommunityBot 111 silver badge asked Jul 30, 2015 at 16:07 Kohányi RóbertKohányi Róbert 10.2k44 gold badges5656 silver badges8383 bronze badges 3

• 1 Why not just animal: res.animal? If you need the interpolation in the middle of a larger string, checkout ES2015 template strings. edit oh OK I see what you're getting at. – Pointy Commented Jul 30, 2015 at 16:12
• Look for JS template engines. Note that asking for off-site resources, libraries, etc. is actually OT for SO. – Dave Newton Commented Jul 30, 2015 at 17:08
• @DaveNewton Well I admit this isn't the best all time SO question :) I really just wanted to put something "out there", so that I (and others) could find it more easily, because I had a hard time finding a painless solution for this. – Kohányi Róbert Commented Jul 30, 2015 at 20:26

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 2

You could JSON.stringify the object, then replace your search value with the actual value, then JSON.parse the result:

function magic(o, a) {
    var j = JSON.stringify(o);
    for (var k in a) {
            j = j.split('${'+k+'}').join(a[k]);
    }
    return JSON.parse(j);
}

I suggest to you a very simple but very fast and understandable template engine: simple-template.js

It consists of 22 lines of code, very simple! Considering that, you will be able to render your config easily!

本文标签： jsonWays to interpolate template variables inside JavaScript objectsStack Overflow