javascript简写常用的12个技巧（可以大大减少你的js代码量）

if (variable1 !== null || variable1 !== undefined || variable1 !== ''){
 let variable2 = variable1;
}

let variable2 = variable1 || '';

//值为null的例子
let variable1 = null;
let variable2 = variable1 || '';
console.log(variable2);
//输出: ''
//值为undefined的例子
let variable1 = undefined;
let variable2 = variable1 || '';
console.log(variable2);
//输出: ''
//正常情况
let variable1 = 'hi there';
let variable2 = variable1 || '';
console.log(variable2);
//输出: 'hi there'

if("undefined" != typeof downlm){ 
if(downlm=="soft"){ 
document.write('成功'); 
} 
}

let a = new Array(); a[0] = "myString1"; a[1] = "myString2"; a[2] = "myString3";

let a = ["myString1", "myString2", "myString3"];

let big;
if (x > 10) {
big = true;
}
else {
big = false;
}

let big = x > 10 ? true : false;

let big = (x > 10);
let x = 3,
big = (x > 10) ? "greater 10" : (x < 5) ? "less 5" : "between 5 and 10";
console.log(big); //"less 5"
let x = 20,
big = {true: x>10, false : x< =10};
console.log(big); //"Object {true=true, false=false}"

let x;
let y;
let z = 3;

let x, y, z=3;

x=x+1;
minusCount = minusCount - 1;
y=y*10;

x++;
minusCount --;
y*=10;

x += y // x=15
x -= y // x=5
x *= y // x=50
x /= y // x=2
x %= y // x=0

var re = new RegExp("\d+(.)+\d+","igm"),
result = re.exrc("padding 01234 text text 56789 padding");
console.log(result);//"01234 text text 56789"

var result = /d+(.)+d+/igm.exec("padding 01234 text text 56789 padding");
console.log(result); //"01234 text text 56789"

if (likeJavaScript === true)

if (likeJavaScript)

let c;
if ( c!= true ) {
// do something...
}

let c;
if ( !c ) {
// do something...
}

function myFunction( myString, myNumber, myObject, myArray, myBoolean ) {
// do something...
}
myFunction( "String", 1, [], {}, true );

function myFunction() {
/* 注释部分
console.log( arguments.length ); // 返回 5
for ( i = 0; i < arguments.length; i++ ) {
console.log( typeof arguments[i] ); // 返回 string, number, object, object, boolean
}
*/
}
myFunction( "String", 1, [], {}, true );

"myString".charAt(0);

"myString"[0];//返回'm'

function x() {console.log('x')};function y() {console.log('y')};
let z = 3;
if (z == 3)
{
x();
} else
{
y();
}

function x() {console.log('x')};function y() {console.log('y')};let z = 3;
(z==3?x:y)();

for (let i = 0; i < 10000; i++) {

for (let i = 0; i < 1e7; i++) {