Like any kind of apps, JavaScript apps also have to be written well.

Otherwise, we run into all kinds of issues later on.

In this article, we’ll look at some tips we should follow when writing JavaScript code.

**Get a Random Number in a Specific Range**

We can get a random number from a specify range with the `Math.random()`

method.

For example, we can write:

```
const min = 2;
condt max = 10;
const x = Math.floor(Math.random() * (max - min + 1)) + min;
```

Since `Math.random()`

only returns a number between 0 and 1, we’ve to multiply what it returns with `max — min + 1`

.

Then we add that to `min`

to make it within range.

**Generate an Array of Numbers with Numbers from 0 to Max**

We can create an array of numbers by using a for loop.

For example, we can write:

```
let numbersArray = [] , max = 100;
for (let i = 1; numbersArray.push(i++) < max);
```

We use the `for`

loop to increment `i`

by 1 with each iteration.

And then we end with we reach `max — 1`

.

`i++`

increments and returns the number we return.

**Generate a Random Set of Alphanumeric Characters**

We can create a random set of alphanumeric characters by using the `toString`

and `substr`

methods.

For instance, we can write:

```
function generateRandomAlphaNum(len) {
let randomString = "";
while (randomString.length < len) {
randomString += Math.random()
.toString(36)
.substr(2);
}
return randomString.substr(0, len);
}
```

We have the `generateRandomAlphaNum`

function.

And we use the `while`

loop to generate the string up to the given `len`

value.

To generate the character we use the `Math.random()`

with the `toString`

and `substr`

calls to create the character.

**Shuffle an Array of Numbers**

We can shuffle an array of number with the `sort`

method.

For example, we can write:

```
const numbers = [5, 2, 4, 3, 6, 2];
numbers = numbers.sort(() => { return Math.random() - 0.5});
```

We return a random number that’s positive or negative so that the order is switched only when it’s positive.

That’s random so we shuffle them.

**A String Trim Function**

We can trim all whitespace with the `replace`

method and some regex.

For example, we can write:

```
str.replace(/^s+|s+$/g, "")
```

We trim all whitespace with the regex.

JavaScript strings also have the `trim`

method to do the trimming.

**Append an Array to Another Array**

To append an array to another array, we can use the spread operator with `push`

.

For example, we can write:

```
array1.push(...array2);
```

We can also use the spread operator without `push`

:

```
const arr = [...arr1, ...arr2];
```

### Transform Arguments into an Array

We can get arguments as an array with the rest operator.

For example, if we have:

```
const foo = (...args) => {}
```

Then whatever we have in `args`

will be an array.

We can pass in anything into `foo`

and it’ll end up in `args`

.

### Conclusion

We can generate random entities with the `Math.random`

method.

Also, we can append items to arrays and get arguments.