[js] apply、call 更多使用实例

 

传入(继承)参数

 

            function sum() {
                return Array.prototype.reduce.call(arguments, function(sum, value) {
                    if (value >= 1 && value <= 9) {
                        return sum + value;
                    } else {
                        return sum;
                    }
                }, 0);
            }

            function multiplication() {
                return Array.prototype.reduce.call(arguments, function(product, value) {
                    return product * value;
                }, 1);
            }

            function filter(min, max) {
                return Array.prototype.slice.call(arguments, 2).filter(function(value) {
                    return value >= min && value <= max;
                });
            }

            function filterNoNumbers() {
                return Array.prototype.filter.call(arguments, function(value) {
                    return typeof value === 'number' && value === value && value !== Number.POSITIVE_INFINITY && value !== Number.NEGATIVE_INFINITY;
                });
            }

            function round(decimals) {
                if (arguments.length === 2) {
                    return arguments[1].toFixed(decimals);
                } else {
                    return Array.prototype.splice.call(arguments, 1).map(function(value) {
                        return value.toFixed(decimals);
                    });
                }
            }
            console.log(sum.apply(null, filter(1, 9, -3, 1, 0, 4, 8, 9, 12))); //22
            console.log(multiplication.apply(null, filter(1, 9, -3, 1, 0, 4, 8, 9, 12))); //288
            console.log(sum.apply(null, filter.apply(null, [1, 9].concat(filterNoNumbers(-3, NaN, 1, 0, "2", 4, 8, 9, 12))))); // 22
            console.log(round.apply(null, [2].concat(sum.apply(null, filter.apply(null, [1, 9].concat(filterNoNumbers(-3, 1.016, 0, 4, NaN, 8.041, '27', 9, 12))))))); // "22.06"

 

#

            function log() {
                console.log.apply(console, arguments);
            };
            log('xx','hah');

 

#

            function addCall(a) {
                var f = function(v) {
                    return v + this.base;
                }
                var b = {
                    base: 2
                };
                return f.call(b, a); //一起做参数传入了f，但是结构是b到a？
                //return f.call(a, b);//一起做参数传入了f，但是结构是a到b？
            }
            console.info(addCall(1)); //3

 

 

 

Array.prototype.slice.call()

[].slice.call()

array.slice(begin[, end])

#常用将多个参数转换为数组然后进行slice，不传begin则取全部

[].slice.call(arguments)

 

Array.prototype.splice.call()

array.splice(start, deleteCount[, item1[, item2[, ...]]])

 只有删除没有了添加功能

第一个参数代表去除0-start的参数，取完

加入第二个代表去除0-start的参数，取deleteCount个

#将多个参数转换为数组然后进行splice

            function round(decimals) {
                if (arguments.length === 2) {
                    return arguments[1].toFixed(decimals);
                } else {
                    return Array.prototype.splice.call(arguments, 1).map(function(value) {
                        return value.toFixed(decimals);
                    });
                }
            }
            console.log(round(2, 1, 2.1, 2.346)); // ["1.00", "2.10", "2.35"]
            console.log(round(2, 1.3)); // "1.30"

 

 

 

 

Math.max.apply()     Math.min.apply()

#数组中的最大值最小值

 

            var numbers = [5, 458, 120, -215, 228, 400, 122205, -85411];
//            var maxInNumbers = Math.max.apply(Math, numbers);
//            var minInNumbers = Math.min.apply(Math, numbers);
//            var maxInNumbers = Math.max.apply(this, numbers);
//            var minInNumbers = Math.min.apply(this, numbers);
            var maxInNumbers = Math.max.apply(null, numbers);
            var minInNumbers = Math.min.apply(null, numbers);
            console.log(maxInNumbers);
            console.log(minInNumbers);

 

 

Object.prototype.toString.call()

#类型判别

           function isArray(value) {
                return Object.prototype.toString.call(value) == '[object Array]';
            }

            function isFunction(value) {
                return Object.prototype.toString.call(value) == '[object Function]';
            }

            function isRegExp(value) {
                return Object.prototype.toString.call(value) == '[object RegExp]';
            }
            console.log(isRegExp(/abc/));

 

 

Array.prototype.push.apply()

#数组之间追加

            var array1 = [12, "foo", {name:"Joe"}, -2458];
            var array2 = ["Doe", 555, 100];
            Array.prototype.push.apply(array1, array2);
            //array1 值为  [12 , "foo" , {name:"Joe"} , -2458 , "Doe" , 555 , 100]

 

Array.prototype.reduce.call()

#将参数转换为数组然后进行reduce

            function sum() {
                return Array.prototype.reduce.call(arguments, function(sum, value) {
                    console.log(sum, value);
                    return sum + value;
                }, 0);
            }
            console.log(sum(1, 4, 8, 9)); //22

 

Array.prototype.filter.call(）

#将多个参数转换成数组然后进行filter

//判别是否是数字
            function filterNoNumbers() {
                return Array.prototype.filter.call(arguments, function(value) {
                    return typeof value === 'number' && value === value && value !== Number.POSITIVE_INFINITY && value !== Number.NEGATIVE_INFINITY;
                });
            }
            filterNoNumbers(-3, NaN, 1, 0, "2", 4, 8, 9, 12); // [-3, 1, 0, 4, 8, 9, 12]