Added Slice.md in array section

arrays/Slice.md

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+# Slice
+
+You have an array of elements and you want to access or require elements upto a certain index. So rather than looping in down to the whole array, we can use inbuilt **slice** method. This method consists of 2 optional parameters (start and end). Let us consider some examples to understand more. 
+
+1. **WITH ONE PARAMTER**
+```javascript
+//An array
+var countries = ['India', 'United States of America', 'United Kingdom', 'Canada', 'Australia'];
+
+//console.log to see the effect
+console.log(countries.slice(2));
+
+//Output will be -  ['United Kingdom', 'Canada', 'Australia'];
+```
+
+When you provide a single parameter in slice method, it will start picking the elements from that parameter (index starts from zero) and prints till the end.
+
+2. Now let's see what happend if we pass **BOTH THE PARAMETERS**
+
+```javascript
+console.log(countries.slice(1,4));
+//Output:  ['United States of America', 'United Kingdom', 'Canada'];
+```
+
+When you pass both the paramter (start and end), slice will start picking elements from 'start' index and prints till 'end-1' index. As you can see from above example (it prints countries from index 1 to 3).
+
+3. As I said, these both parameters are **optional**, what would happen if you do not pass any parameter.
+```javascript
+console.log(countries.slice());
+//Output: ['India', 'United States of America', 'United Kingdom', 'Canada', 'Australia'];
+```
+
+In that case, it will print your whole array.
+
+You can assign a new variable to store the results from slice.
+```javascript
+var newArray = countries.slice(1,4);
+console.log(newArray);
+//Output: ['United States of America', 'United Kingdom', 'Canada'];
+```