Node.js

Using Pre-defined JSON Templates

See more JSON Examples

Demonstrates how to predefine a JSON template, and then use it to emit JSON with variable substitutions.

Note: This example requires Chilkat v9.5.0.67 or greater.

Node.js

NODEJS_PRELUDE

function chilkatExample() {

    //  One way to create JSON is to do it in a straightforward manner:
    var json = new chilkat.JsonObject();
    json.EmitCompact = false;
    json.UpdateString("id","0001");
    json.UpdateString("type","donut");
    json.UpdateString("name","Cake");
    json.UpdateString("image.url","images/0001.jpg");
    json.UpdateInt("image.width",200);
    json.UpdateInt("image.height",200);
    json.UpdateString("thumbnail.url","images/thumbnails/0001.jpg");
    json.UpdateInt("thumbnail.width",32);
    json.UpdateInt("thumbnail.height",32);
    console.log(json.Emit());

    //  The JSON created by the above code:

    //  	{ 
    //  	  "id": "0001",
    //  	  "type": "donut",
    //  	  "name": "Cake",
    //  	  "image": { 
    //  	    "url": "images/0001.jpg",
    //  	    "width": 200,
    //  	    "height": 200
    //  	  },
    //  	  "thumbnail": { 
    //  	    "url": "images/thumbnails/0001.jpg",
    //  	    "width": 32,
    //  	    "height": 32
    //  	  }
    //  	}

    //  An alternative is to predefine a template, and then use it to emit with variable substitutions.
    //  For example:

    var jsonTemplate = new chilkat.JsonObject();
    jsonTemplate.UpdateString("id","{$id}");
    jsonTemplate.UpdateString("type","donut");
    jsonTemplate.UpdateString("name","{$name}");
    jsonTemplate.UpdateString("image.url","{$imageUrl}");
    //  The "i." indicates that it's an integer variable.
    jsonTemplate.UpdateString("image.width","{$i.imageWidth}");
    jsonTemplate.UpdateString("image.height","{$i.imageHeight}");
    jsonTemplate.UpdateString("thumbnail.url","{$thumbUrl}");
    jsonTemplate.UpdateString("thumbnail.width","{$i.thumbWidth}");
    jsonTemplate.UpdateString("thumbnail.height","{$i.thumbHeight}");
    //  Give this template a name.
    jsonTemplate.Predefine("donut");

    //  --------------------------------------------------------------------------
    //  OK, the template is defined.  Defining a template can be done once
    //  at the start of your program, and you can discard the jsonTemplate object (it
    //  doesn't need to stick around..)

    //  Now we can create instances of the JSON object by name:
    var jsonDonut = new chilkat.JsonObject();
    jsonDonut.EmitCompact = false;
    jsonDonut.LoadPredefined("donut");
    console.log(jsonDonut.Emit());

    //  The output is this:

    //  	{ 
    //  	  "id": "{$id}",
    //  	  "type": "donut",
    //  	  "name": "{$name}",
    //  	  "image": { 
    //  	    "url": "{$imageUrl}",
    //  	    "width": "{$i.imageWidth}",
    //  	    "height": "{$i.imageHeight}"
    //  	  },
    //  	  "thumbnail": { 
    //  	    "url": "{$thumbUrl}",
    //  	    "width": "{$i.thumbWidth}",
    //  	    "height": "{$i.thumbHeight}"
    //  	  }
    //  	}

    //  Finally, we can substitute variables like this:
    var donutValues = new chilkat.Hashtable();
    donutValues.AddStr("id","0001");
    donutValues.AddStr("name","Cake");
    donutValues.AddStr("imageUrl","images/0001.jpg");
    donutValues.AddInt("imageWidth",200);
    donutValues.AddInt("imageHeight",200);
    donutValues.AddStr("thumbUrl","images/thumbnails/0001.jpg");
    donutValues.AddInt("thumbWidth",32);
    donutValues.AddInt("thumbHeight",32);

    //  Emit with variable substitutions:
    var omitEmpty = true;
    console.log(jsonDonut.EmitWithSubs(donutValues,omitEmpty));

    //  Output:

    //  	{ 
    //  	  "id": "0001",
    //  	  "type": "donut",
    //  	  "name": "Cake",
    //  	  "image": { 
    //  	    "url": "images/0001.jpg",
    //  	    "width": 200,
    //  	    "height": 200
    //  	  },
    //  	  "thumbnail": { 
    //  	    "url": "images/thumbnails/0001.jpg",
    //  	    "width": 32,
    //  	    "height": 32
    //  	  }
    //  	}

    //  Change some of the values:
    donutValues.AddStr("id","0002");
    donutValues.AddStr("imageUrl","images/0002.jpg");
    donutValues.AddStr("thumbUrl","images/thumbnails/0002.jpg");

    console.log(jsonDonut.EmitWithSubs(donutValues,omitEmpty));

    //  Output:

    //  	{ 
    //  	  "id": "0002",
    //  	  "type": "donut",
    //  	  "name": "Cake",
    //  	  "image": { 
    //  	    "url": "images/0002.jpg",
    //  	    "width": 200,
    //  	    "height": 200
    //  	  },
    //  	  "thumbnail": { 
    //  	    "url": "images/thumbnails/0002.jpg",
    //  	    "width": 32,
    //  	    "height": 32
    //  	  }
    //  	}

}

chilkatExample();