Javascript

• Utility types

Popular code styles

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• Standard
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Function find() returns the first value of an array satisfying a given condition.

let array1 = [1,4,6,8,12];
let found = array1.find(el => {
   return el > 10
  }
);
//found = 12

Function map() applies a specified function to each element in the array.

var array1 = [1, 4, 9, 16];
const map1 = array1.map(x => Math.pow(x,2));
//map1=[1,16,81,256]

For more complicated functions

array1.map(x => {
  //stuff with x
  return x;
})

Function reduce() executes a given reducer function on every element of the array returning a single value. It consists of accumulator getting information from each element of the array consequently.

let array1 = [1, 2, 3, 4];
let r = array1.reduce((acc, elem) => acc + elem)
//r = 10

Initial value initVal could be specified by

array1.reduce((acc,elem) => acc + elem, initVal);

Function every() checks if a given condition applies to every element of the array.

const array1 = [true, false, true];
if(array1.every(Boolean)) {
//all conditions met
}

Returns a subset of the array satisfying certain conditions

const data = ["hotel","california", "baby"];
let newdata = data.filter(e => e.length > 5);

Constructor shortcut without manually assigning properties to the new instance.

export class CartItem {
    id: number;
    name: string;
    description: string;
    unitPrice: number;
    coverPhoto: string;
    quantity: number;
 
    constructor(data: any) {
        Object.assign(data)
    }
}

New instance of the class with specified properties can now be created by

CartItem({'id': 1, 'name': 'Paper towel', ...})

Template literals

const x = 10
console.log("x = ${x}")
const y = `x = ${x}`

Multiline string

const s = "SELECT * \
          FROM table \
          WHERE ...";
const t = `one \
           two`

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