JS Functional functions

1. isArrayLike
2. map, each
3. bloop

JavaScriptFunc/FunctionalFunctions.js

@@ -127,4 +127,16 @@ function compose() {
         }
         return result;
     }
-}
+}
+
+// getLength
+function getLength(list) {
+    return list == null ? void 0 : list.length;
+}
+
+// isArrayLike
+var isArrayLike = function(list) {
+    var MAX_ARRAY_INDEX = Number.MAX_SAFE_INTEGER;
+    var length = getLength(list);
+    return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
+};

JavaScriptFunc/MakingUnderscoreFuncs/bloop.js

@@ -0,0 +1,31 @@
+// bloop: bind loop 를 통해 함수를 만들기
+
+var _ = require("./underscore.js");
+
+function bloop(new_data, body) {
+    return function(data, iteratee) {
+        var result = new_data(data);
+        if (_.isArrayLike(data)) {
+            for (var i = 0, len = data.length; i < len; i++) {
+                body(iteratee(data[i], i, data), result);
+            }
+        } else {
+            for (var key in data) {
+                if (data.hasOwnProperty(key)) {
+                    body(iteratee(data[key], key, data), result);
+                }
+            }
+        }
+        return result;
+    };
+}
+
+var map = bloop(function() {
+    return [];
+}, function(val, obj) {
+    return obj.push(val);
+});
+
+console.log(map([ 1, 2, 3 ], function(v){
+    return v * 2;
+}));

JavaScriptFunc/MakingUnderscoreFuncs/each.js

@@ -0,0 +1,17 @@
+var _ = require("./underscore.js");
+
+var each = function(data, iteratee) {
+    if (_.isArrayLike(data)) {
+        for (var i = 0, len = data.length; i < len; i++) {
+            iteratee(data[i], i , data);
+        }
+    } else {
+        for (var key in data) {
+            if (data.hasOwnProperty(key)) iteratee(data[key], key, data);
+        }
+    }
+
+    return data;
+};
+
+each([ 1, 2, 3 ], console.log);

JavaScriptFunc/MakingUnderscoreFuncs/map.js

@@ -0,0 +1,50 @@
+// supporters
+var MAX_ARRAY_INDEX = Number.MAX_SAFE_INTEGER;
+
+// getLength
+function getLength(list) {
+    return list == null ? void 0 : list.length;
+}
+
+// isArrayLike
+var isArrayLike = function(list) {    
+    var length = getLength(list);
+    return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
+};
+// // supporters
+
+var map = function(data, iteratee) {
+    var new_list = [];
+    if (isArrayLike(data)) {
+        for (var i = 0, len = data.length; i < len; i++) {
+            new_list.push(iteratee(data[i], i, data));
+        }
+    } else {
+        for (var key in data) {
+            if (data.hasOwnProperty(key)) new_list.push(iteratee(data[key], key, data));
+        }
+
+    }
+    return new_list;
+};
+
+var arr1 = map([1, 2, 3], function(v){
+    return v * 2;
+});
+var arr2 = map({a: 3, b: 2, c: 1}, function(v){
+    return v * 2;
+});
+
+console.log(arr1);
+console.log(arr2);
+
+// underscore.js에서는 세 번째 인자로 iteratee에서 사용할 this를 전달할 수 있지만
+// this를 적용한 새로운 함수를 만드는 것은 작은 부하가 있다.
+// 그 함수를 실행할 때도 부하가 생긴다. 반복하는 횟수가 많을수록 부하도 쌓이므로
+// 개발자에게 iteratee에서의 this 다루기를 위임하고 최대한 깨끗한 함수만 받도록 하자.
+
+var arr3 = map([1, 2, 3], function(v){
+    return v * this;
+}.bind(5));
+
+console.log(arr3);

JavaScriptFunc/MakingUnderscoreFuncs/underscore.js

@@ -0,0 +1,90 @@
+(function() {
+    var _ = function(){};
+
+    var root = this;
+
+    var _ = function(obj) {
+        if (obj instanceof _) return obj;
+        if (!(this instanceof _)) return new _(obj);
+        this._wrapped = obj;
+    };
+
+    // Export the Underscore object for **Node.js**, with
+    // backwards-compatibility for the old `require()` API. If we're in
+    // the browser, add `_` as a global object.
+    if (typeof exports !== 'undefined') {
+        if (typeof module !== 'undefined' && module.exports) {
+            exports = module.exports = _;
+        }
+        exports._ = _;
+    } else {
+        root._ = _;
+    }
+
+
+    var MAX_ARRAY_INDEX = Number.MAX_SAFE_INTEGER;
+
+    // getLength
+    function getLength(list) {
+        return list == null ? void 0 : list.length;
+    }
+
+    // isArrayLike
+    _.isArrayLike = function(list) {    
+        var length = getLength(list);
+        return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
+    };
+
+    // identity
+    _.identity = function(v) {
+        return v;
+    };
+    _.idtt = _.identity;
+
+    // args
+    _.args0 = _.identity;
+    _.args1 = function(a, b) {
+        return b;
+    };
+
+    // values
+    _.values = function(list) {
+        return _.map(list, _.identity);
+    };
+
+    // keys
+    _.keys = function(list) {
+        return _.map(list, _.args1);
+    };
+
+    // map
+    _.map = function(data, iteratee) {
+        var new_list = [];
+        if (_.isArrayLike(data)) {
+            for (var i = 0, len = data.length; i < len; i++) {
+                new_list.push(iteratee(data[i], i, data));
+            }
+        } else {
+            for (var key in data) {
+                if (data.hasOwnProperty(key)) new_list.push(iteratee(data[key], key, data));
+            }
+
+        }
+        return new_list;
+    };
+
+    // each
+    _.each = function(data, iteratee) {
+        if (_.isArrayLike(data)) {
+            for (var i = 0, len = data.length; i < len; i++) {
+                iteratee(data[i], i , data);
+            }
+        } else {
+            for (var key in data) {
+                if (data.hasOwnProperty(key)) iteratee(data[key], key, data);
+            }
+        }
+
+        return data;
+    };
+}.call(this));

JavaScriptFunc/MakingUnderscoreFuncs/values_keys.js

@@ -0,0 +1,27 @@
+var _ = require("./underscore.js");
+
+// identity
+var identity = function(v) {
+    return v;
+};
+var idtt = _.identity;
+
+// args
+var args0 = _.identity;
+var args1 = function(a, b) {
+    return b;
+};
+
+// values
+var values = function(list) {
+    return _.map(list, _.identity);
+};
+
+// keys
+var keys = function(list) {
+    return _.map(list, _.args1);
+};
+
+console.log(values({ id: 5, name: "MK", age: 30 }));
+console.log(keys({ id: 5, name: "MK", age: 30 }));
+console.log(keys([ 1, 2, 3 ]));

JavaScriptFunc/isArrayLike.js

@@ -0,0 +1,30 @@
+// _.each, _.map 등에서 사용하는 객체는 2가지에서 4가지 정도다
+// {}, [], arguments, ArrayLike
+
+// 1. {}
+var d1 = { name: 'MK', age: 30 };
+
+// 2. []
+var d2 = [ 1, 2, 3 ];
+
+// 3. arguments
+var d3 = function() {
+    return arguments;
+}(1, 2, 3);
+
+// 4. ArrayLike
+//var d4 = $("div");
+var d5 = { length: 3 };
+d5[0] = 1, d5[1] = 2, d5[2] = 3;
+var d6 = "hi";
+
+
+function getLength(list) {
+    return list == null ? void 0 : list.length;
+}
+
+var isArrayLike = function(list) {
+    var MAX_ARRAY_INDEX = Number.MAX_SAFE_INTEGER;
+    var length = getLength(list);
+    return typeof length == 'number' && length >= 0 && length <= MAX_ARRAY_INDEX;
+};