some important js build in methods 🚀

lgope · lgope · commit 5d13dca347c6 · 2020-05-20T23:47:01.000+06:00
diff --git a/BuildIn-Methods/indexOf.js b/BuildIn-Methods/indexOf.js
@@ -0,0 +1,8 @@
+let str = 'Hello world, welcome to the JS Universe.';
+console.log(str.indexOf('welcome')); // 13
+console.log(str.indexOf('wall')); // -1
+
+const fruits = ['Orange', 'Pineapple', 'Apple', 'Melon'];
+console.log(fruits.indexOf('Melon')); // 3
+
+console.log(fruits.indexOf('klkljkh')); // -1
diff --git a/BuildIn-Methods/lastIndexOf.js b/BuildIn-Methods/lastIndexOf.js
@@ -0,0 +1,4 @@
+const fruits = ['Orange', 'Pineapple', 'Apple', 'Melon'];
+console.log(fruits.lastIndexOf('Melon')); // 3
+
+console.log(fruits.lastIndexOf('klkljkh')); // -1
diff --git a/BuildIn-Methods/length.js b/BuildIn-Methods/length.js
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+const fruits = ['Orange', 'Pineapple', 'Apple', 'Melon'];
+console.log(fruits.length); // 4
+
+let str = 'Hello world, welcome to the JS Universe.';
+console.log(str.length); // 40
diff --git a/BuildIn-Methods/map.js b/BuildIn-Methods/map.js
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+// The map() method creates a new array populated with the results of calling a provided function on every element in the calling array.
+
+const array = [1, 4, 9, 16, 15, 48];
+
+// pass a function to map
+const map1 = array.map(ar => ar * 2);
+
+console.log(map1);
+// expected output: Array [2, 8, 18, 32]
+
+function myFunction(num) {
+  return num * 10;
+}
+
+let newArray = array.map(myFunction);
+console.log(newArray);
diff --git a/BuildIn-Methods/reduce.js b/BuildIn-Methods/reduce.js
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+// The reduce() method executes a reducer function (that we provide) on each element of the array, resulting in single output value.
+
+const array = [1, 2, 3, 4, 5];
+const reducerFunc = (accumulator, currentValue) => accumulator + currentValue;
+
+// 1 + 2 + 3 + 4 + 5
+console.log(array.reduce(reducerFunc));
+// expected output: 15
+
+// 5 + 1 + 2 + 3 + 4 + 5
+console.log(array.reduce(reducerFunc, 5));
+// expected output: 20
diff --git a/BuildIn-Methods/slice.js b/BuildIn-Methods/slice.js
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+// The slice() method returns a shallow copy of a portion of an array into a new array object selected from begin to end (end not included) where begin and end represent the index of items in that array. The original array will not be modified.
+
+const array = [1, 2, 3, 4, 5];
+
+const anotherArr = array.slice(1, 4);
+
+console.log(anotherArr);
+
+console.log(array.slice(2, 5));
diff --git a/BuildIn-Methods/toString.js b/BuildIn-Methods/toString.js
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+let num = 10;
+let n = num.toString();
+
+console.log(typeof num); // number
+
+console.log(typeof n); // string
diff --git a/BuildIn-Methods/typeOf.js b/BuildIn-Methods/typeOf.js
@@ -0,0 +1,8 @@
+console.log(typeof 44); // number
+
+console.log(typeof 'something'); // string
+
+console.log(typeof true); // boolean
+
+let num = 12;
+console.log(typeof num); // number
