简写技巧
当同时声明多个变量时，可简写成一行
//longhandlet x;let y = 20; //shorthandlet x, y = 20;
利用解构，可为多个变量同时赋值
//longhandlet a, b, c;a = 5;b = 8;c = 12;//shorthandlet [a, b, c] = [5, 8, 12];
巧用三元运算符简化if else
//longhand let marks = 26; let result; if (marks >= 30) { result = 'pass'; } else { result = 'fail'; } //shorthand let result = marks >= 30 ? 'pass' : 'fail';
使用||运算符给变量指定默认值
本质是利用了||运算符的特点，当前面的表达式的结果转成布尔值为false时，则值为后面表达式的结果
//longhandlet imagepath;let path = getimagepath();if (path !== null && path !== undefined && path !== '') { imagepath = path;} else { imagepath = 'default.jpg';}//shorthandlet imagepath = getimagepath() || 'default.jpg';
使用&&运算符简化if语句
例如某个函数在某个条件为真时才调用，可简写
//longhandif (isloggedin) { gotohomepage(); }//shorthandisloggedin && gotohomepage();
使用解构交换两个变量的值
let x = 'hello', y = 55;//longhandconst temp = x;x = y;y = temp;//shorthand[x, y] = [y, x];
适用箭头函数简化函数
//longhandfunction add(num1, num2) { return num1 + num2;}//shorthandconst add = (num1, num2) => num1 + num2;
需要注意箭头函数和普通函数的区别
使用字符串模板简化代码
使用模板字符串代替原始的字符串拼接
//longhandconsole.log('you got a missed call from ' + number + ' at ' + time);//shorthandconsole.log(`you got a missed call from ${number} at ${time}`);
多行字符串也可使用字符串模板简化
//longhandconsole.log('javascript, often abbreviated as js, is a\n' + 'programming language that conforms to the \n' + 'ecmascript specification. javascript is high-level,\n' + 'often just-in-time compiled, and multi-paradigm.' );//shorthandconsole.log(`javascript, often abbreviated as js, is a programming language that conforms to the ecmascript specification. javascript is high-level, often just-in-time compiled, and multi-paradigm.` );
对于多值匹配，可将所有值放在数组中，通过数组方法来简写
//longhandif (value === 1 || value === 'one' || value === 2 || value === 'two') { // execute some code}// shorthand 1if ([1, 'one', 2, 'two'].indexof(value) >= 0) { // execute some code}// shorthand 2if ([1, 'one', 2, 'two'].includes(value)) { // execute some code }
巧用es6对象的简洁语法
例如，当属性名和变量名相同时，可直接缩写为一个
let firstname = 'amitav';let lastname = 'mishra';//longhandlet obj = {firstname: firstname, lastname: lastname};//shorthandlet obj = {firstname, lastname};
使用一元运算符简化字符串转数字
//longhandlet total = parseint('453');let average = parsefloat('42.6');//shorthandlet total = +'453';let average = +'42.6';
使用repeat()方法简化重复一个字符串
//longhandlet str = '';for(let i = 0; i < 5; i ++) { str += 'hello ';}console.log(str); // hello hello hello hello hello// shorthand'hello '.repeat(5);// 想跟你说100声抱歉！'sorry\n'.repeat(100);
使用双星号代替math.pow()
//longhandconst power = math.pow(4, 3); // 64// shorthandconst power = 4**3; // 64
使用双波浪线运算符（~~）代替math.floor()
//longhandconst floor = math.floor(6.8); // 6// shorthandconst floor = ~~6.8; // 6
需要注意，~~仅适用于小于2147483647的数字
巧用扩展操作符（...）简化代码
简化数组合并
let arr1 = [20, 30];//longhandlet arr2 = arr1.concat([60, 80]); // [20, 30, 60, 80]//shorthandlet arr2 = [...arr1, 60, 80]; // [20, 30, 60, 80]
单层对象的拷贝
let obj = {x: 20, y: {z: 30}};//longhandconst makedeepclone = (obj) => { let newobject = {}; object.keys(obj).map(key => { if(typeof obj[key] === 'object'){ newobject[key] = makedeepclone(obj[key]); } else { newobject[key] = obj[key]; }});return newobject;}const cloneobj = makedeepclone(obj);//shorthandconst cloneobj = json.parse(json.stringify(obj));//shorthand for single level objectlet obj = {x: 20, y: 'hello'};const cloneobj = {...obj};
寻找数组中的最大和最小值
// shorthandconst arr = [2, 8, 15, 4];math.max(...arr); // 15math.min(...arr); // 2
使用for in和for of来简化普通for循环
let arr = [10, 20, 30, 40];//longhandfor (let i = 0; i < arr.length; i++) { console.log(arr[i]);}//shorthand//for of loopfor (const val of arr) { console.log(val);}//for in loopfor (const index in arr) { console.log(arr[index]);}
简化获取字符串中的某个字符
let str = 'jscurious.com';//longhandstr.charat(2); // c//shorthandstr[2]; // c
移除对象属性
let obj = {x: 45, y: 72, z: 68, p: 98};// longhanddelete obj.x;delete obj.p;console.log(obj); // {y: 72, z: 68}// shorthandlet {x, p, ...newobj} = obj;console.log(newobj); // {y: 72, z: 68}
使用arr.filter(boolean)过滤掉数组成员的值falsey
let arr = [12, null, 0, 'xyz', null, -25, nan, '', undefined, 0.5, false];//longhandlet filterarray = arr.filter(function(value) { if(value) return value;});// filterarray = [12, "xyz", -25, 0.5]// shorthandlet filterarray = arr.filter(boolean);// filterarray = [12, "xyz", -25, 0.5]
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以上就是总结分享20个提升效率的javascript简写技巧的详细内容。