ES6 new method

One 、includes

Determine whether the string contains some characters , Or whether the array contains an element

1、 Basic usage

console.log('abc'.includes('a'));//true
console.log('abc'.includes('d'));//false
console.log([1,2,3].includes(1));//true
console.log([1,2,3].includes('1'));//false

2、 The second parameter
Indicates where to start the search , The default is 0

console.log('abc'.includes('a',1));//false

Two 、padStart() and padEnd()

Complete the length of the string

1、 Basic usage

console.log('x'.padStart(5,'ab'));//ababx
console.log('x'.padEnd(5,'ab'));//xabab

2、 matters needing attention

• The length of the original string , Equal to or greater than the maximum length , The original string will not be subtracted , String completion does not take effect , Returns the original string

console.log('xxx'.padEnd(2,'ab'));//xxx

• The sum of the length of the complement string and the original string exceeds the maximum length , Truncate the complement string exceeding the number of digits , The original string does not move

console.log('abc'.padStart(10, '0123456789'));//0123456abc

• If you omit the second parameter , By default, space is used to complete the length

3、 ... and 、trimStart() and trimEnd()

Clear the space at the beginning or end of the string , The space in the middle will not be cleared

Four 、 Array of Array.from()

Convert other data types to arrays
All traversable
Array 、 character string 、Set、Map、riodeList、arguments
Have length Property

1、 Basic usage

console.log(Array.from('str'));//[ 's', 't', 'r' ]
const obj = {
    
	'0':'a',
	'1':'b',
	name: 'Alex',
	length: 3
};
console.log(Array.from(obj));//[ 'a', 'b', undefined ]

2、 The second parameter
Act like an array map Method , Used to process each element , Put the processed value into the returned array

console.log(
	[1,2].map(value => {
    return value * 2})
);//[ 2, 4 ]
console.log(Array.from('12', value => value * 2));//[ 2, 4 ]

5、 ... and 、find() and findIndex()

find(): Find an immediate return that meets the conditions
findIndex(): Find one that meets the conditions , Return to an index immediately

1、 Basic usage

console.log(
	[1,5,10,15].find((value) =>{
    
	return value > 9;
	})
);//10

console.log(
	[1,5,10,15].findIndex((value) =>{
    
	return value > 9;
	})
);//2

6、 ... and 、Object.assign()

Merge objects
The following of the same attribute will overwrite the previous
You can merge multiple objects

const apple = {
    
	color: ' Red ',
	shape: ' circular ',
	taste: ' sweet '
};
const pen = {
    
	color: ' black ',
	shape: ' cylindrical ',
	use: ' Write '
};

console.log(Object.assign(apple,pen));
//{ color: ' black ', shape: ' cylindrical ', taste: ' sweet ', use: ' Write ' }
console.log(apple)//{ color: ' black ', shape: ' cylindrical ', taste: ' sweet ', use: ' Write ' }
console.log(Object.assign(apple,pen)===apple)//true

7、 ... and 、Object.keys). Object.values() and Object.entries()

Get the key value of the object

const person = {
    
	name: 'Alex',
	age: 18
};
console.log(Object.keys(person));//[ 'name', 'age' ]
console.log(Object.values(person));//[ 'Alex', 18 ]
console.log(Object.entries(person));//[ [ 'name', 'Alex' ], [ 'age', 18 ] ]