node 陣列常用方法
阿新 • • 發佈:2019-01-05
//length 可變 var arr = [] arr.length = 10 arr[1] = 2 console.log(arr) arr.length = 8 console.log(arr) //index 可以超過length arr[12] = "f" console.log(arr) //push/pop 從尾部讀取 arr = [1, 2, 3, 4, 5, 6] arr.push(12) console.log(arr) let a = arr.pop() console.log(a, arr) arr.push(...["a", "b", "c"]) console.log(arr) //shift /unshift 從頂部移除新增 arr.shift() console.log(arr) arr.unshift("1", ...[10, "l"]) console.log(arr) //splice 擷取並插入 let arrnew = arr.splice(0, 3, "new", "new1") console.log(arrnew, "\\n", arr) //reverse 逆序 arr.reverse() console.log(arr) //sort 排序 arr.splice(0, 3) arr.sort() console.log(arr) //new //arr=new Array() //Object.values Object.keys Object.entries 取值 取key 資料[[key,value]] console.log(Object.values(arr)) console.log(Object.keys(arr)) console.log(Object.entries(arr)) let str = "1,2,34,56,," arr = str.split(",") console.log(arr) //concat 陣列連線 返回連線後的陣列 arr = arr.concat("new", ...["a", "b", 'c']) console.log(arr) //slice arr1 = arr.slice(1, 3) console.log(arr1) //map 類似於foreach arr.map((v, k, e) => console.log(v)) //求平方 temp = [1, 2, 3] temp = temp.map(v => v * v) console.log(temp) arr.map((v, k) => console.log(`${k}==${v}`)) //filter 篩選 console.log(arr) arr = arr.filter((v, k) => v > 1) // arr.filter((v, k) => v > 1).forEach((v, k, s) => { // console.log(s) // }) console.log(arr) //every 是否所有滿足條件 console.log("is null:", arr.every(v => !v)) //some 是否有一個滿足 console.log("have >1:", arr.some(v => v > 1)) // includes 包含 console.log("hava 2:", arr.includes('2')) //foreach 與map 區別 map 會返回新陣列 console.log(arr) arr.forEach(v => v * v) console.log(arr) //reduce 累加器 arr = arr.map(v => parseInt(v)) let total = arr.reduce((base, num) => base + num, 3) console.log(total) // arr = ["apple", "orange", "apple", "orange", "pear", "orange"]; // function getWordCnt() { // return arr.reduce(function (prev, next) { // prev[next] = (prev[next] + 1) || 1; // return prev; // }, {}); // } // console.log(getWordCnt()); //find let t = arr.find(v => v = 2) console.log(t) let index = arr.indexOf(34) console.log(index) str = arr.join(',') console.log(str)