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():

[]

JavaScript

          if (condition) {
  // do this
  // ...and that
  // ...and that
}
        

if (condition) doSomething()

! :

if (n < 0) {alert(`Power ${n} is not supported`);}

          if (n < 0)
  alert(`Power ${n} is not supported`);
        

if (n < 0) alert(`Power ${n} is not supported`);

          if (n < 0) {
  alert(`Power ${n} is not supported`);
}
        

if (cond) return null

          //  ` 
let str = `
  ECMA International's TC39 is a group of JavaScript developers,
  implementers, academics, and more, collaborating with the community
  to maintain and evolve the definition of JavaScript.
`;
        

if :

          if (
  id === 123 &&
  moonPhase === 'Waning Gibbous' &&
  zodiacSign === 'Libra'
) {
  letTheSorceryBegin();
}
        

1 80 120

2(4)

2 4 ( Tab)

          show(parameters,
     aligned, //  5 
     one,
     after,
     another
  ) {
  // ...
}
        

          function pow(x, n) {
  let result = 1;
  //              <--
  for (let i = 0; i < n; i++) {
    result *= x;
  }
  //              <--
  return result;
}
        

JavaScript

JavaScript StandardJS

"continue"

if :

          for (let i = 0; i < 10; i++) {
  if (cond) {
    ... // <- 1
  }
}
        

          for (let i = 0; i < 10; i++) {
  if (!cond) continue;
  ...  // <- 
}
        

if/else return

          function pow(x, n) {
  if (n < 0) {
    alert("Negative 'n' not supported");
  } else {
    let result = 1;

    for (let i = 0; i < n; i++) {
      result *= x;
    }

    return result;
  }
}
        

          function pow(x, n) {
  if (n < 0) {
    alert("Negative 'n' not supported");
    return;
  }

  let result = 1;

  for (let i = 0; i < n; i++) {
    result *= x;
  }

  return result;
}
        

2n < 0

          // 
function createElement() {
  ...
}

function setHandler(elem) {
  ...
}

function walkAround() {
  ...
}

// 
let elem = createElement();
setHandler(elem);
walkAround();
        

          // 
let elem = createElement();
setHandler(elem);
walkAround();

// ---  ---

function createElement() {
  ...
}

function setHandler(elem) {
  ...
}

function walkAround() {
  ...
}
        

linter

Linter

JSLint linter 1
JSHint JSLint
ESLint linter

ESLint

linter :

ESLint :

Node.js
npm install -g eslint ESLint (npm Node.js )
JavaScript() .eslintrc
ESlint /

.eslintrc :

          {
  "extends": "eslint:recommended",
  "env": {
    "browser": true,
    "node": true,
    "es6": true
  },
  "rules": {
    "no-console": 0,
    "indent": 2
  }
}
        

"extends" eslint:recommended

ESLint /

Webhttp://eslint.org/docs/user-guide/getting-started

linter : linter linter ()

linter

IDE linter ESLint

Bad style

          function pow(x,n)
{
  let result=1;
  for(let i=0;i<n;i++) {result*=x;}
  return result;
}

let x=prompt("x?",''), n=prompt("n?",'')
if (n<=0)
{
  alert(`Power ${n} is not supported, please enter an integer number greater than zero`);
}
else
{
  alert(pow(x,n))
}
        

          function pow(x,n)  // <- 
{  // <- 
  let result=1;   // <- = 
  for(let i=0;i<n;i++) {result*=x;}   // <- 
  // { ... } 
  return result;
}

let x=prompt("x?",''), n=prompt("n?",'') // <-- ,
// 2 ; 
if (n<0)  // <- (n < 0) 
{   // <- 
  //  -- 12
  alert(`Power ${n} is not supported, please enter an integer number greater than zero`);
}
else // <- "} else {" 1
{
  alert(pow(x,n))  // spaces  ; 
}
        

          function pow(x, n) {
  let result = 1;

  for (let i = 0; i < n; i++) {
    result *= x;
  }

  return result;
}

let x = prompt("x?", "");
let n = prompt("n?", "");

if (n < 0) {
  alert(`Power ${n} is not supported,
    please enter an integer number greater than zero`);
} else {
  alert( pow(x, n) );
}
        