[js] 数字数组的一点Array Helpers

#1

            Object.assign(Array.prototype, {
                square() {
                    return this.map(n => n * n);
                },
                cube() {
                    return this.map(n => Math.pow(n, 3));
                },
                sum() {
                    return this.reduce((p, n) => p + n, 0);
                },
                average() {
                    return this.reduce((p, n) => p + n, 0) / this.length;
                },
                even() {
                    return this.filter(n => !(n % 2));
                },
                odd() {
                    return this.filter(n => n % 2);
                }
            });

 

 #2

            Array.prototype.square = function() {
                return this.map(function(n) {
                    return n * n;
                });
            }
            Array.prototype.cube = function() {
                return this.map(function(n) {
                    return n * n * n;
                });
            }
            Array.prototype.sum = function() {
                return this.reduce(function(a, b) {
                    return a + b;
                }, 0);
            }
            Array.prototype.average = function() {
                return this.sum() / this.length;
            }
            Array.prototype.even = function() {
                return this.filter(function(item) {
                    return 0 == item % 2;
                });
            }
            Array.prototype.odd = function() {
                return this.filter(function(item) {
                    return 0 != item % 2;
                });
            }

 

#3

            Array.prototype.square = function() {
                var temp = [],
                    l = this.length;
                for (var i = 0; i < l; i++) {
                    temp[i] = this[i] * this[i];
                }
                //console.log(temp);
                //console.log(this);
                return temp;
            };
            Array.prototype.cube = function() {
                var temp = [],
                    l = this.length;
                for (var i = 0; i < l; i++) {
                    temp[i] = this[i] * this[i] * this[i];
                }
                //console.log(temp);
                //console.log(this);
                return temp;
            };
            Array.prototype.sum = function() {
                if (this.length === 0) {
                    return NaN;
                }
                var temp = 0,
                    l = this.length;
                for (var i = 0; i < l; i++) {
                    temp += this[i];
                }
                //console.log(temp);
                //console.log(this);
                return temp;
            };
            Array.prototype.average = function() {
                if (this.length === 0) {
                    return NaN;
                }
                var l = this.length,
                    temp = this.sum() / l;
                //console.log(temp);
                //console.log(this);
                return temp;
            };
            Array.prototype.even = function() {
                if (this.length === 0) {
                    return NaN;
                }
                var l = this.length,
                    temp = [];
                for (var i = 0; i < l; i++) {
                    if (!(this[i] % 2)) {
                        temp.push(this[i]);
                    }
                }
                //console.log(temp);
                //console.log(this);
                return temp;
            };
            Array.prototype.odd = function() {
                if (this.length === 0) {
                    return NaN;
                }
                var l = this.length,
                    temp = [];
                for (var i = 0; i < l; i++) {
                    if (this[i] % 2) {
                        temp.push(this[i]);
                    }
                }
                //console.log(temp);
                //console.log(this);
                return temp;
            };

#test

            var numbers = [1, 2, 3, 4, 5];
            console.log(numbers.square());
            console.log(numbers.cube());
            console.log(numbers.sum());
            console.log(numbers.average());
            console.log(numbers.even());
            console.log(numbers.odd());
            var empty = [];
            console.log(empty.average());
            console.log(empty.sum());