add find, filter, findIndex method

Author: munnasorder

filter.js

@@ -0,0 +1,25 @@
+const myArray = [1,2,3,4,5,6,7,8,9];
+
+// example 1
+Array.prototype.myFind = function(cb) {
+    let result = [];
+    for (let i = 0, length = this.length; i < length; i++) {
+        if (cb(this[i], i, this)) result.push(this[i]);
+    };
+    return result;
+}
+const result = myArray.filter((doc, i, arr) => doc > 3);
+console.log(result)
+// output [ 4, 5, 6, 7, 8, 9 ]
+
+// example 2
+function myOwnFilter(arr, cb) {
+    let result = [];
+    for (let i = 0, length = arr.length; i < length; i++) {
+        if (cb(arr[i], i, arr)) result.push(arr[i]);
+    }
+    return result;
+}
+const result2 = myOwnFilter(myArray, (doc, i, arr) => doc > 5);
+console.log(result2)
+// output [ 6, 7, 8, 9 ]

find.js

@@ -0,0 +1,24 @@
+const myArray = [1,2,3,4,5,6,7,8,9];
+
+// example 1
+Array.prototype.myFind = function(cb) {
+    for (let i = 0, length = this.length; i < length; i++) {
+        if (cb(this[i], i, this)) return this[i];
+    };
+};
+
+const result = myArray.myFind((doc, i, arr) => doc > 9);
+console.log(result);
+// output undefined
+
+
+// example 2
+function myOwnMap(arr, cb) {
+    for (let i = 0, length = arr.length; i < length; i++) {
+        if (cb(arr[i], i, arr)) return arr[i];
+    }
+}
+
+const result2 = myOwnMap(myArray, (doc, i, arr) => doc > 2);
+console.log(result2);
+// output 3

findIndex.js

@@ -0,0 +1,24 @@
+const myArray = [1,2,3,4,5,6,7,8,9];
+
+// example 1
+Array.prototype.myFindIndex = function(cb) {
+    for (let i = 0, length = this.length; i < length; i++) {
+        if (cb(this[i], i, this)) return i;
+    }
+    return -1;
+}
+const result = myArray.myFindIndex((doc, i, arr) => doc === 5);
+console.log(result)
+// output 4
+
+// example 2
+function myOwnFindIndex(arr, cb) {
+    for (let i = 0; i < arr.length; i++) {
+        if (cb(arr[i], i, arr[i])) return i;
+    }
+    return -1;
+}
+
+const result2 = myOwnFindIndex(myArray, (doc, i, arr) => doc === 8);
+console.log(result2);
+// output 7