(Node.js) Using Pre-defined JSON Templates

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.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOSX, and ARM

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

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();