Nodejs Array Reduce reduce(f, value)

Method Source Code

// 6_5_Confusion/*from  w  ww . j  a v  a 2  s .co  m*/
var is_array_01 = function (value) {
   return value &&
      typeof value === 'object' &&
      value.constructor === Array;
};

var is_array = function (value) {
   return value &&
      typeof value === 'object'  &&
      typeof value.length === 'number'  &&
      typeof value.splice === 'function'  &&
      !(value.propertyIsEnumerable('length'));
};

// 6_6_Methods
// Array.method('reduce', function(f, value){
Array.prototype.reduce = function(f, value){
   var i;
   for (i = 0; i < this.length; i++) {
      value = f(this[i],value);
   }
   return value;
};

// 6_7_dim
Array.dim = function(dimension, initial) {
   var a = [], i;
   for (i = 0; i < dimension; i++) {
      a[i] = initial;
   }
   return a;
};

// 6_7_matrix
Array.matrix = function (m, n, initial) {
   var a, i, j, mat = [];
   for (i = 0; i < m; i += 1) {
      a = [];
      for (j = 0; j < n; j += 1) {
         a[j] = initial;
      }
      mat[i] = a;
   }
   return mat;
};

Related

1. reduce(f, inital)

   var arr = [0,1,2,3,4];
   var sum = function(x, y) { return x + y; };
   Array.prototype.reduce = function(f, inital) {
       var acc = initial;
       for (var i = 0; i < this.length; i++) {
           acc = f(acc, this[i]);
       return acc;
   };
   ...
   

2. reduce(f, initial)

   var arr = [0,1,2,3,4];
   var sum = function(total, newValue) { return total + newValue; };
   Array.prototype.reduce = function(f, initial) {
       var acc = initial;
       for (var i = 0; i < this.length; i++) {
           acc = f(acc, this[i]);
       return acc;
   };
   ...
   

3. reduce(f, value)

   Array.prototype.reduce = function (f, value) { 
       for (var i = 0; i < this.length; i++) { 
           value = f(this[i], value)
       return value
   

4. reduce(f, value)

   Array.prototype.reduce = function (f, value) {
     for (var i = 0, len = this.length; i < len; i++) {
       value = f(this[i], value);
     return value;
   };
   var superheroes = ['superman', 'iron man', 'spiderman', 'batman'];
   var totalLength = superheroes.reduce(function (elem, acc) {
     return elem.length + acc;
   ...
   

5. reduce(f, value)

   var data = [ 4, 8, 15, 16, 23, 42 ];
   Array.prototype.reduce = function(f, value) {
       var i;
       for (i = 0; i < this.length; i += 1) {
           value = f(this[i], value);
       return value;
   };
   var add = function(a, b) {
   ...
   

6. reduce(f, value)

   Array.prototype.reduce = function(f, value) {
       var i;
       for (i = 0; i < this.length; i += 1) {
           value = f(this[i], value);
       return value;
   };
   var data = [ 4, 8, 15, 16, 23, 42 ];
   var add = function(a, b) {
   ...
   

7. reduce(fn, initial)

   Array.prototype.reduce = function(fn, initial)
       var r, i;
       initial ? r = initial : r = this[0];
       for (i=1;i<this.length;i++)
           r = fn(r, this[i]);
       return r;
   ...
   

8. reduce(fn, initialValue)

   Array.prototype.reduce = function (fn, initialValue) {
     let acc = initialValue
     for (var i = 0; i < this.length; i++) {
       acc = fn(acc, this[i], i)
     return acc
   Array.prototype.forEach = function (fn) {
     this.reduce((acc, curr, i) => {
   ...
   

9. reduce(fun /* , initial */)

   if (!Array.prototype.reduce) {
     Array.prototype.reduce = function(fun ) {
       var len = this.length >>> 0;
       if (typeof fun != "function")
         throw new TypeError();
       if (len == 0 && arguments.length == 1)
         throw new TypeError();
       var i = 0;
       if (arguments.length >= 2) {
   ...