1. Print a string multiple times

In javascript you could print a string multiple times by using a loop, but you can also do it like this myString.repeat(3); and that will print the string 3 times.

2. Check the length of an array

If you are checking the length of an array like myArray.length > 0, you can actually only check for myArray.length. There is no need to add the greater than 0 part.

3. Check if a string is null or undefined

You can do it like this if (myString !== undefined && myString !== null) {} or like this if (myString) {}

4. Add items into array

Probably the best way to add items into array is like this myArray.push(1);, but you could also do it like myArray[myArray.length] = 1; or const newArray = myArray.concat([1]);. Since the first 2 methods modify the existing array, they are a lot faster than the last method which is creating a new constant.

5. Sort strings with accented characters

Did you know that the .sort() function does not work well with non ASCII characters like é or ú? If you run ['o', 'W', 'ö', 'ä'].sort(); you will get ["W", "o", "ä", "ö"] which is not the right order. To compare strings with accented characters you can do it like this ['o', 'W', 'ö', 'ä'].sort(Intl.Collator().compare) or like this ['o', 'W', 'ö', 'ä'].sort((a, b) => a.localeCompare(b)); which will print ["ä", "o", "ö", "W"]