JS30

Array Cardio 指南

soyaine的笔记

效果

简单的介绍一些Array.prototype的方法， 比如 Array.prototype.filter, Array.prototype.map, Array.prototype.reduce等（这些都被常用于higher order function） 在我以前学的CMPS112 Comparative Languages 里很像，都是functional language. 因为，我比较熟悉这些方法，我就列举一些例子.

CMPS112笔记

要点

• filter
• reduce
• map
• sort
• ES6 array matching

知识点

• filter

Example: 去重(去除array中相同的元素)

var uniq = function (array){
    return array.filter((item, index) => array.indexOf(item) == index)
}

备注：The indexOf() method returns the first index at which a given element can be found in the array, or -1 if it is not present.

indexOf链接 filter链接

• reduce

Example:

const totalYears = inventors.reduce((total, inventor) => {
      return total + (inventor.passed - inventor.year);
    }, 0);

Fun Fun Function Reduce

• map

 const fullNames = inventors.map(inventor => `${inventor.first} ${inventor.last}`);

Fun Fun Function Map

• sort && ES6 destructuring

Example:

const alpha = people.sort((lastOne, nextOne) => {
      const [aLast, aFirst] = lastOne.split(', ');
      const [bLast, bFirst] = nextOne.split(', ');
      return aLast > bLast ? 1 : -1;
    });

假如 const people = "['Beck, Glenn', 'Becker, Carl']", 在这种情况下，

lastOne = 'Beck, Glenn'
nextOne = 'Becker, Carl'
aLast = 'Beck'
aFirst = 'Glenn'
bLast = 'Becker'
bFirst = 'Carl'

为什么我们要使用destructuring?

Example:

makeSound({weight: 23, sound:'woof'})

// without destructuring

function makeSound(options){
	var species = options.species || 'animal'
	var sound = options.sound
	console.log('The' + species + ' says' + sound + '!')
}

//with destructuring

functiong makeSound({species="animal", sound}){
	console.log('The' + species + ' says' + sound + '!')
}

destructuring 可以使代码更简洁，易读

ES 6 array matching

[Destucturing]（https://www.youtube.com/watch?v=PB_d3uBkQPs&t=330s）