CODEWITHSUNDEEP
javascriptangulartypescript
Z. Bagley
Z. Bagley

Reputation: 9270

JavaScript (TypeScript/Angular): Shortest/Fastest method to set object keys/values based on previous logic?

I'm attempting to fill an array with objects where the objects are all the same, and the keys are determined from a predefined item. I know I can do this with multiple if...else, but that seems to be a long method to use and was hoping for something more condensed and/or efficient without using external libraries.

Current method to fill array with hardcoded Objects:

fillArray(arr,n) {
  while(arr.length < n) {
    arr.push({
        'x': Math.round(Math.random(),
        'name': 'item' + arr.length + 1
    });
  }
}

Example of what I'd like to achieve using an if:

fillArray(arr, n, type) {
  while(arr.length < n) {
    if ( type === 'type1' ) {
      arr.push({
        'x': Math.round(Math.random(),
        'name': 'item' + arr.length + 1
      });
    } else if ( type === 'type2') {
      arr.push({
        'x': Math.round(Math.random(),
        'y': Math.round(Math.random(),
        'name': 'item' + arr.length + 1
      });
    }
  }
}

In my application I will use this type of method with a dozen if items, and there will be similar methods as well. I do not wish to apply any static typing for these items, since my application may require object keys to be dynamically added.

An idea I had that I can't seem to get a complete idea in my head would be somehow pre-defining an array of objects, and then using a find to somehow apply each item in the array as a type.

Psuedo-code (untested):

myTypes = [{
  type: 'type1', keys: ['x', 'name']},
  {type: 'type2', keys: ['x', 'y', 'name']
}];
fillArray(arr,n, type) {
  let currentType = this.myTypes.find( myTypes => myTypes.type === type).keys
  while(arr.length < n) {
    // add for loop to iterate over each key/value here separately
  }
}

Would this type of method work, be efficient, and is a reasonable practice to this approach? Are there any other standard practices for this type of array population with dynamic keys?

Upvotes: 1

Views: 151

Answers (1)

Estus Flask
Estus Flask

Reputation: 222626

Moving to dynamic properties with object like keys will harm type safety. Since TypeScript is a primary language, this is an important concern. Also, keys doesn't allow to control property values.

It can be a hierarchy of classes or some factory functions:

class Type1 {
  x = ...;
  name = ...;
}

class Type2 extends Type1 {
  y = ...;
}

const typesMap = { type1: Type1, type2: Type2 };

fillArray(arr, n, type) {
  while(arr.length < n) {
    arr.push(new typesMap[type])
  }
}

The difference from the original code is that it won't work properly if type is incorrect or missing, which may or may not be desirable.

Upvotes: 2

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