JavaScript

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.

JavaScript

// One way to create JSON is to do it in a straightforward manner:
var json = new CkJsonObject();
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 CkJsonObject();
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 CkJsonObject();
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 CkHashtable();
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
// 	  }
// 	}