json template engine in node.js

Question

I have a json template like the following:

[
  {
    "type":"foo",
    "config":"{config}"
  },
  {
    "type":"bar",
    "arrConfig":"{arrConfig}"
  }
]

While i have a backing model like:

{
  "config": {
    "test1": "value1",
    "test2": "value2"
  },
  "arrConfig": [
    "test3": {
      "key1": "val1"
    },
    "test4": {
      "key1": "val1"
    }
  ]
}

I'm wondering if there are any node modules out there which will automatically take these two and transform the placeholders in the template. So the output would look like:

[
  {
    "type":"foo",
    "config":{
      "test1": "value1",
      "test2": "value2"
    }
  },
  {
    "type":"bar",
    "arrConfig": [
      "test3": {
        "key1": "val1"
      },
      "test4": {
        "key1": "val1"
      }
    ]
  }
]

I mean a quick & dirty solution would to just do text replacement on the JSON. You could write your own function to recursively traverse an object hierarchy and replace matching text values. — qxz
– qxz, Commented Aug 6, 2016 at 1:04
I think it's a bit more complex that since the placeholder values might be an object, array, string, number etc... So accordingly i will have to replace it — user320550
– user320550, Commented Aug 6, 2016 at 4:28

Tiago Engel · Accepted Answer · 2016-08-06 14:25:31Z

6

JSON.stringify accepts a replacer param that you could use to do it.

This should work:

var template = [
  {
    "type":"foo",
    "config":"{config}"
  },
  {
    "type":"bar",
    "arrConfig":"{arrConfig}"
  }
];


var data = {
  "config": {
    "test1": "value1",
    "test2": "value2"
  },
  "arrConfig": {
    "test3": {
      "key1": "val1"
    },
    "test4": {
      "key1": "val1"
    }
  }
};

var replacer = function (key, val) {
   if (typeof val === 'string' && val.match(/^{(.+)}$/)) {
     return data[val.replace(/[{|}]/g, '')]
   }
   return val;
 }

 console.log(JSON.stringify(template, replacer));

And if you want to transform it back to an object you can use JSON.parse

edited Aug 6, 2016 at 14:25

answered Aug 6, 2016 at 14:07

Tiago Engel

3,6712 gold badges19 silver badges22 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

qxz · Accepted Answer · 2016-08-06 08:53:45Z

Here is a function to traverse an object hierarchy and replace template strings, as specified:

// modifies the object passed, and returns the same object
function applyTemplate(template, backing) {
  for (var i in template) {
    var m = /^{(.+)}$/.exec(template[i]);
    if (m && backing[m[1]]) {
      // replace with a deep clone of the value from the backing model
      template[i] = JSON.parse(JSON.stringify(backing[m[1]]));
    } else if (template[i] && "object" == typeof template[i]) {
      // traverse down recursively
      applyTemplate(template[i], backing);
    }
  }
  return template;
}

var template = [
  {
    "type":"foo",
    "config":"{config}"
  },
  {
    "type":"bar",
    "arrConfig":"{arrConfig}"
  }
];

var backing = {
  "config": {
    "test1": "value1",
    "test2": "value2"
  },
  "arrConfig": {
    "test3": {
      "key1": "val1"
    },
    "test4": {
      "key1": "val1"
    }
  }
};

applyTemplate(template, backing);
console.log(JSON.stringify(template, null, 2));

Plus a proof-of-concept using raw JSON text replacement (not robust, don't actually use this; but works for the vast majority of scenarios):

function applyTemplateStr(template, backing) {
  template = JSON.stringify(template);
  for (var key in backing) {
    template = template.split('"{'+key+'}"').join(JSON.stringify(backing[key]));
  }
  return JSON.parse(template);
}

Kevindra · Accepted Answer · 2018-12-22 05:26:55Z

1

You can use Mustache, like so:

var template = [
  {
    type: "foo",
    config: "{{config}}"
  }
];

var data = {
  config: "hello"
};

const Mustache = require("mustache");

function render(template, data) {
  return Mustache.render(JSON.stringify(template), data);
}

var output = render(template, data);
console.log(output);  // [{"type":"foo","config":"hello"}]

answered Dec 22, 2018 at 5:26

Kevindra

1,7624 gold badges25 silver badges46 bronze badges

Collectives™ on Stack Overflow

json template engine in node.js

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related