提升代码幸福度，五个技巧减少js开发中的if else语句

function fn(name) {
    if(!name){
        name = '听风是风';
    };
    console.log(name);
};
fn();//听风是风
fn('行星飞行');//行星飞行

function fn(name) {
    name = name || '听风是风';
    console.log(name);
};
fn();//听风是风
fn('行星飞行');//行星飞行

function fn() {
    console.log(1);
};
true || fn(); //不执行
false && fn(); //不执行
false || fn(); //1
true && fn() //1

let name = false;
function fn() {
    console.log(1);
};
//if
if (!name) {
    fn();//1
};
//短路
!name && fn();//1

function fn(param) {
    param = param || 1;
    console.log(param);
};
fn(0); //1
fn(null); //1
fn(false); //1

//使用形参默认值
function fn1(param = 1) {
    console.log(param);
};
fn1(); //1
fn1(0); //0
fn1(null); //null
fn1(false); //false

let blo = true;
let num;
if (blo) {
    num = 1;
} else {
    num = 0;
};
console.log(num);//1

//三元运算符
blo =false;
blo ? num = 1 : num = 0;
console.log(num);//0

let blo = true;
let fn = function () {
    console.log(1);
};
//if
if (blo) {
    fn(); //1
};

//三元
blo ? fn() : null;//1

let fn = function () {
    let flo = true;
    if (flo) {
        return 1;
    } else {
        return 2;
    };
};
let f = fn(); //1

let fn1 = function () {
    let flo = true;
    //三元
    return flo ? 1 : 2;
};
let f1 = fn1();//1

let result = 0;
function add(n){
    result += n
    return n>=2 ? add(n-1) : result;
};
let num = add(10);//55

let i = 5;
if (i > 0) {
    //执行语句超过2句
    console.log(1);
    i = 0;
};

let name = 'B';
//if else if
if (name === 'A') {
    console.log('a');
} else if (name === 'B') {
    console.log('b');
} else if (name === 'C') {
    console.log('c');
} else {
    console.log('d');
};

//switch case
switch (name) {
    case 'A':
        console.log('a');
        break;
    case 'B':
        console.log('b');
        break;
    case 'C':
        console.log('c');
　　　　　break;
    default:
        console.log('d');
};

let name = 'B';
//if else if
if (name === 'A' || name === 'B') {
    console.log(1);
} else if (name === 'C') {
    console.log(2);
} else {
    console.log(3);
};

//switch case
switch (name) {
    case 'A':
    case 'B':
        console.log(1);
        break;
    case 'C':
        console.log(2);
　　　　　break;　
    default:
        console.log(3);
};

function del() {
    //删除操作
};

function add() {
    //新增
};

function update() {
    //更新
};

function process(operateType) {
    if (operateType === 'del') {
        del()
    } else if (operateType === 'add') {
        add()
    } else if (operateType === 'update') {
        update()
    };
};
process('del');//删除

function del() {
    //删除操作
};

function add() {
    //新增
};

function update() {
    //更新
};
let typeFn = {
    'del': del,
    'add': add,
    'update': update
};

function process(operateType) {
    typeFn[operateType]();
};
process('del'); //删除

function process(operateType, status) {
    if (operateType === 'del' && status === 1) {
        del()
    } else if (operateType === 'add'&& status === 2) {
        add()
    } else if (operateType === 'update'&& status === 3) {
        update()
    };
};

let typeFn = {
    'del_1': del,
    'add_2': add,
    'update_3': update
};

function process(operateType,status) {
    typeFn[`${operateType}_${status}`]();
};
process('del',1); //删除

let typeFn = new Map([
    ['del_1', function () {/*do something*/ }],
    ['add_2', function () {/*do something*/ }],
    ['update_3', function () {/*do something*/ }],
]);

function process(operateType, status) {
    typeFn.get(`${operateType}_${status}`)();
};
process('del', 1); //删除

function youAreMyHero(experience) {
    if (experience < 100) {
        return '萌新';
    } else if (experience < 200 && experience >= 100) {
        return '骑士';
    } else if (experience < 300 && experience >= 200) {
        return '英雄';
    } else if (experience >= 300) {
        return '传说';
    };
};
let level = youAreMyHero(351); //传说

function youAreMyHero(param) {
    let experience = [300, 200, 100];
    let level = ['传说', '英雄', '骑士', '萌新'];

    for (var i = 0; i < experience.length; i++) {
        if (param >= experience[i]) {
            return level[i];
        };
    };
    return level[i];
};

let level = youAreMyHero(250); //英雄