Reading-Notes

Class 03 Summary :

map() —-> loop on the array and return output array with the same length of the input array.(the same number of values in the input array).
To loop through an array and display each value we can use map(). by doing this (arr.map(item =>{console.log(item);})
In the list item, each list needs a unique key(id).
The key purpose is to specify the changing or adding or removing items in the array.by giving it a unique id.

Spread Operator is syntax use 3 dots to expand repeated object to arguments in list, add items to an array, combining arrays or objects.
1. “Copy array”
  1. “seperate array to small arguments”.
  2. “use math function”
  3. “add item to list”
const array1=[‘a’,’b’,’c’]

const array2=[‘m’,’n’,’o’]

const array3=[…array1, …array2]

array3 —> [‘a’,’b’,’c’,’m’,’n’,’o’]

let studentStudy ={ study:’Engineering’, place:’LTUC’ };

let studentInfo = { …student, …studentStudy };

the output ——> studentInfo ={ name:’Sukina’, age:31, study:’Engineering’, place:’LTUC’ }

First step to pass functions between components : create function where the status will change
The increment function take object or which we want to change , call map method to loop inside object name and increment the count inside the object which passed. then return the object.and then update the state object.
To pass a method from a parent to Child : increment =(this.increment)

inside the personal object.

this.props.increment (this.props.name);