8 Must-Know JavaScript Array Methods
01 .forEach()
Executes a provided function once for each array element.
// .forEach()
const emojis = ['football','run','pizza']
emojis.forEach(emoji => {
console.log(`I love ${emoji}`) //注意 `` 這個符號
})
02 .map()
Creates a new array populated with the results of calling a provided function on every element.
// .map()
const emojis = ['football','run','pizza']
const result = emojis.map(emoji => {
return emoji + emoji
})
console.log(result)
//result : [ 'footballfootball', 'runrun', 'pizzapizza' ]
03 .filter()
Creates a new array with all elements that pass the test implemented by the provided function.
// .filter()
const emojis = ['football','run','pizza','basketball']
const pet = emojis.filter(emoji => {
return emoji == 'football' || emoji == 'run'
})
console.log(pet)
//result : [ 'football', 'run' ]
04 .concat()
Creates a new array by merging two or more arrays.
// .concat()
const fruits = ['apple','banana']
const vegetables = ['carrot','tomato']
const result = fruits.concat(vegetables)
console.log(result)
//result : [ 'apple', 'banana', 'carrot', 'tomato' ]
05 .find()
Returns the value of the first array element that satisfies the provided test function, or undefined
//.find()
const emojis = ['sun','moon','pizza','basketball']
const moon = emojis.find(emoji => {
return emoji == 'moon'
})
console.log(moon)
//result : moon
06 .push()
Adds the specified elements to the end of an array.
//.push()
const emojis = ['donut','cake','cookies']
emojis.push('ice cream')
console.log(emojis)
//result : [ 'donut', 'cake', 'cookies', 'ice cream' ]
07 .pop()
Removes the last element from an array and returns it.
//.pop()
const emojis = ['donut','cake','cookies']
const lastEmoji = emojis.pop()
console.log(lastEmoji)
console.log(emojis)
/*result :
cookies
[ 'donut', 'cake' ]
*/
08 .includes()
Determines whether an array includes a certain value or not.
//.includes()
const emojis = ['donut','cake','cookies']
const hasDonut = emojis.includes('donut')
console.log(hasDonut)
const hasIceCream = emojis.includes('ice cream')
console.log(hasIceCream)
/*#result :
true
false
*/
转载请注明来源，欢迎对文章中的引用来源进行考证，欢迎指出任何有错误或不够清晰的表达。可以邮件至 kimfei2014@gmail.com