es6语法 高阶函数 filter map reduce

const nums = [10, 20, 30, 100, 200, 40, 50]
// 1 filter函数的使用
// let newNums = nums.filter(function (n) {
//   return n < 100
// })
// console.log(newNums)

// 2 map函数的使用
// let new2Nums = newNums.map(function (n) {
//   return n * 2
// })
// console.log(new2Nums)

// 2 reduce函数的使用
// let total = newNums.reduce(function (preValue, n) {
//   return preValue + n
// }, 0)

let total = nums.filter(n => n < 100).map(n => n * 2).reduce((pre, n) => pre + n)
console.log(total)

// 高阶函数reduce
return this.books.reduce(function (preValue, book) {
  return preValue + book.price * book.count
}, 0)

<pre><div class="hljs"><code class="lang-js"><span class="hljs-keyword">const</span> nums = [<span class="hljs-number">10</span>, <span class="hljs-number">20</span>, <span class="hljs-number">30</span>, <span class="hljs-number">100</span>, <span class="hljs-number">200</span>, <span class="hljs-number">40</span>, <span class="hljs-number">50</span>] <span class="hljs-comment">// 1 filter函数的使用</span> <span class="hljs-comment">// let newNums = nums.filter(function (n) {</span> <span class="hljs-comment">// return n &lt; 100</span> <span class="hljs-comment">// })</span> <span class="hljs-comment">// console.log(newNums)</span> <span class="hljs-comment">// 2 map函数的使用</span> <span class="hljs-comment">// let new2Nums = newNums.map(function (n) {</span> <span class="hljs-comment">// return n * 2</span> <span class="hljs-comment">// })</span> <span class="hljs-comment">// console.log(new2Nums)</span> <span class="hljs-comment">// 2 reduce函数的使用</span> <span class="hljs-comment">// let total = newNums.reduce(function (preValue, n) {</span> <span class="hljs-comment">// return preValue + n</span> <span class="hljs-comment">// }, 0)</span> <span class="hljs-keyword">let</span> total = nums.<span class="hljs-title function_">filter</span>(<span class="hljs-function"><span class="hljs-params">n</span> =&gt;</span> n &lt; <span class="hljs-number">100</span>).<span class="hljs-title function_">map</span>(<span class="hljs-function"><span class="hljs-params">n</span> =&gt;</span> n * <span class="hljs-number">2</span>).<span class="hljs-title function_">reduce</span>(<span class="hljs-function">(<span class="hljs-params">pre, n</span>) =&gt;</span> pre + n) <span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(total) </code></div></pre> <pre><div class="hljs"><code class="lang-js"><span class="hljs-comment">// 高阶函数reduce</span> <span class="hljs-keyword">return</span> <span class="hljs-variable language_">this</span>.<span class="hljs-property">books</span>.<span class="hljs-title function_">reduce</span>(<span class="hljs-keyword">function</span> (<span class="hljs-params">preValue, book</span>) { <span class="hljs-keyword">return</span> preValue + book.<span class="hljs-property">price</span> * book.<span class="hljs-property">count</span> }, <span class="hljs-number">0</span>) </code></div></pre>