Uncle Tom's 6-Way JS Topic

Uncle Tom's 6-way JavaScript programming problem

Look at Uncle Tom's blog, which has an article (poke here) at the end of the 6 programming questions, so I also try, we can try first.

1. Find the largest element in a numeric array (using the Math.max function)

123	vara = [1, 2, 3, 6, 5, 4];varans = Math.max.apply(null, a);console.log(ans);  // 6

This is a clever use of apply, if not an array, is a lot of numbers to find the maximum value, we know that can be:

12	varans = Math.max(1, 2, 3, 4, 5, 6); console.log(ans); // 6

The second parameter of apply is an array, which is not converted.

There is also an implementation using eval+tostring:

123	vara = [1, 2, 3, 6, 5, 4];var ans = eval( ‘Math.max(‘+ a.toString() + ‘)‘);console.log(ans); // 6

2. Convert a numeric array into a function array (each function pops up the corresponding number)

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var a = [1, 2, 3, 4, 5, 6];var len = a.length;for(var i = 0; i < len; i++) {  var num = a[i];  (function(num) {    var f = function() {      console.log(num);    };    a[i] = f;  })(num);}for(var i = 0; i < len; i++)  a[i]();// 1// 2// 3// 4// 5// 6

I think this is to give n a tag, pop the corresponding tag corresponding to the number is a type of problem, with a closure to save the variable to memory.

3. Sort an object array (sorting criteria is the number of attributes per element object)

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var a = {  name: ‘hanzichi‘,  age: 10,  location: ‘china‘};var b = {  name: ‘curry‘};var c = {  name: ‘kobe‘,  sex: ‘male‘};Object.prototype.getLength =  function() {  var num = 0;  for(var key in this) {    if(this.hasOwnProperty(key))      num++;  }  return num;};var arr = [a, b, c];arr.sort(function(a, b) {  return a.getLength() > b.getLength();});console.log(arr);

This problem is not difficult, array sorting, of course, sort, sorting criteria is the number of properties of the object, you can write a function calculation, note may be judged by hasOwnProperty.

4. Use JavaScript to print out the number of Fibonacci (without using global variables)

123456

(function(a, b) {  varc = a + b;  console.log(c);  if(c > 100) return;  arguments.callee(b, c);})(-1, 1);

This question is not clear, is the Fibonacci sequence of the first n? or the nth item ...

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function fn(n) {  var a = [];  a[0] = 0, a[1] = 1;  for(var i = 2; i < n; i++)    a[i] = a[i - 1] + a[i - 2];  for(var i = 0; i < n; i++)    console.log(a[i]);}fn(5); // 10表示需要的斐波那契数列个数// 0// 1// 1// 2// 3

Instead of using global variables, I write them in a function. It's a local variable, right? What do you think?

5, to achieve the following syntax functions: var a = (5). Plus (3). Minus (6); 2

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number.prototype.plus = function (a) {    Code class= "javascript keyword" >return this + A;  number.prototype.minus = function (a) {    return this - A;  var a = (5). Plus (3). Minus (6); console.log (a); //2

Add the extension method directly on the number object, it is not good in legend, but I can not think of a better way ...

6, to achieve the following syntax function: var a = Add (2) (3) (4); 9

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function add(a) {  var temp = function(b) {    return add(a + b);  }  temp.valueOf = temp.toString = function() {    return a;  };  return temp;}var ans = add(2)(3)(4);console.log(ans); // 9

For valueof and ToString, refer to "valueof and ToString" for details.

　　See also a very elegant way of writing (from Gaubee):

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functionadd(num){  num += ~~add;  add.num = num;  return add;}add.valueOf = add.toString = function(){return add.num};varans = add(3)(4)(5)(6);  // 18alert(ans);

Uncle Tom's 6-Way JS Topic