# Arrays

Spread synax allows iterables to be expanded in places where one or more arguments are expected.

function sum(x, y, z) {
    return x + y + z;
}

const numbers = [1, 2, 3];

sum(...numbers);

// this is the pre-ES6 way
sum.apply(null, numbers);

Spread also provides a succinct way to help create a new array by adding a new part to another one.

var newBrands = ['tesla', 'BYD'];
var brands = ['ford', 'honda', ...newBrands, 'bmw']

It can copy arrays

var arr1 = ['a', 'b', 'c'];
var arr2 = [...arr1] // like arr1.slice()
arr2.push('d')

console.log(arr1) // ['a', 'b', 'c']
console.log(arr2) // ['a', 'b', 'c', 'd']

It can concat arrays

https://codepen.io/ozywuli/pen/rrdREZ?editors=1010

# Objects

Copy or clone enumerable properties in objects

var obj1 = { name: 'oscar', age: 28 } var obj2 = { name : 'ozy', age: 25 }

var cloneObj = { ...obj1 } var mergedObj = { ...obj1, ...obj2 }

Merge objects

# Rest

• Rest is for destructuring.
• It's the opposite of spread, which expands an array into its elements, whereas rest collects multiple elements and condenses them into a single element.
• You would use the spread operator as a parameter in a function
• arrays in rest parameters can be destructured

function cars(...[a, b, c]) {
    console.log(a);
    console.log(b);
    console.log(c);
}

cars('ford', 'honda', 'bmw');

• difference between rest parameters and the arguments object
  • rest parameters are only the ones that haven't been given a separate name / arguments object contains all arguments passed into the function
  • rest is an array where as arguments is an object
  • arguments has methods for itself

# References

https://stackoverflow.com/questions/33898512/spread-operator-vs-rest-parameter-in-es2015-es6 https://stackoverflow.com/questions/33898512/spread-syntax-vs-rest-parameter-in-es2015-es6