Today I learn

TIL

## The --depth=14 option just tells Git to pull down only the last 14 commits. This makes the download much smaller and faster.

git clone --depth=14 https://github.com/xxx/xxx

## typeof method in javascript

typeof 1;  // number
typeof "1"; // string
typeof null; // object
typeof undefined; // undefined
typeof this; // object
typeof typeof // Unexpected end of input

## Closures:  is a special kind of object that combines two things: a function, and the environment in which that function was 
created. The environment consists of any local variables that were in-scope at the time that the closure was created. 

var add = (function() {
	var num =0;
	function count(){
		num += 1;
		return num;
	}
	return count;
})();

add(); // 1
add(); // 2

## Memoization: keep previous results to reduce the amount of work for function such as Fibonacci

var fibonacci = (function() {
  var memo = {};

  function f(n) {
    var value;

    if (n in memo) {
      value = memo[n];
    } else {
      if (n === 0 || n === 1)
        value = n;
      else
        value = f(n - 1) + f(n - 2);

      memo[n] = value;
    }

    return value;
  }

  return f;
})();