Common

Closure

A closure is an inner function that has access to the variables in the outer enclosing function scope chain

function outer() {
  var outerVal = 'value';

  function inner() {
    console.log(outerVal); // value
  }
}

Hoisting

// function declarations
fd(); // YA!!!

function fd() {
  console.log('YA!!!');
}

// function expressions
fe(); // TypeError: .....

var fe = function() {
  console.log('NO!!!');
};

Scope

Javascript does not support block level scoping

if (true) {
  var test = 'value';
}

console.log(test); // value

Support block level scopes via the let keyword

if (true) {
  let test = 'value';
}
console.log(test); // SyntaxError: ......

Call & Apply

Both call() & apply() methods calls a function with a given this value, call() accpet an argument list, apply() acceps a single array of arguments

Borrow method

// Borrow method from Array.prototype
function transform() {
    var prefix = arguments[0];
    var args = Array.prototype.slice.call(arguments, 1);
    return args.toString().replace(/,/g, prefix);
}

console.log(transform('.', 'first', 'second', 'third'));
// first.second.third

References

PreviousELKNextReact.js

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