JavaScript의 범위

글로벌 범위

예시:

var globalVariable = "I am a global variable";

let globalVariableDeclaredWithLet =
  "I am a global variable declared with let keyword";

const globalConstant = "I am a global constant";

function globalFunction() {
  console.log("I am a global function");
}

기능 또는 로컬 범위

예시:

function globalFunction() {
  var localVariable = "I am a local variable";

  let localVariableDeclaredWithLet = "I am a local variable declared with let";

  function localFunction() {
    console.log("I am a local function and I can be called within this function only");
  }

  localFunction(); //  I am a local function and I can be called within this function only
}
// invoking localFunction outside the function
localFunction(); // ReferenceError: localFunction is not defined.

블록 범위:

예시:

if(true) {
  let blockVariable = "I am a block variable";
  let blockFunction = () {
    console.log("I am a block function");
  }
  // blockFunction can be called here
  blockFunction(); //I am a block function
}
// blockFunction cannot be called outside the block
blockFunction(); //ReferenceError: blockFunction is not defined

'var'의 이상한 동작

예시:

if (true) {
  var iAmWeird = "I am weird and you can access me from outside this block.";
}

//  iAmWeird can be accessed outside the block.
console.log(iAmWeird); // I am weird and you can access me from outside this block.

키워드 없이 선언됨

예시:

if (true) {
  iAmWeird = "I am weird and you can access me from outside this block.";

  function weirdFunction() {
    console.log("I am a weird function and you can call me from outside this block");
  }
}

console.log(iAmWeird); // I am weird and you can access me from outside this block.

weirdFunction(); // I am a weird function and you can call me from outside this block

let과 const

예시:

if (true) {
  let iAmWeird =
    "I am not weird and you cannot access me from outside this block.";

  const weirdFunction = function () {
    console.log("I am  not a weird function and you cannot call me from outside this block");
  };
}

console.log(iAmWeird); // ReferenceError: iAmWeird is not defined.
weirdFunction(); // ReferenceError: weirdFunction is not defined.