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# Useful JavaScript Tips — Numbers and String Whitespaces

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 to write JavaScript code faster and better.

### Check if a Number is Finite

The `isFinite` method lets us check if a value is a finite number or not.

For instance:

``````Number.isFinite(1)
``````

returns `true` .

On the other hand:

``````Number.isFinite(1)
``````

returns `false` .

### Format a Decimal Number into a String

We can use the `toFixed` method to format a decimal number into a string.

For instance, we can write:

``````(20.22).toFixed()
``````

and get `'20'` .

Also, we can pass in the number of decimal digits we want to keep by writing:

``````(20.22).toFixed(1)
``````

and get `“20.2”` .

### Format a Number into a Language Sensitive String

The `toLocaleString` method lets us get a string that has a number formatted according to the locale.

For instance, we can write:

``````(20.22).toLocaleString('fr-ca')
``````

Then we get `“20,22”` .

### Format a Number into Exponential Notation

The `toExponential` method lets us convert a number into a string that’s in exponential notation.

For instance, we can write:

``````(21.22).toExponential()
``````

Then we get `“2.122e+1”` .

### Change the Number of Decimal Digits of a Number

The `toPrecision` method formats a number into a string that has the given number of decimal digits.

For instance, we can write:

``````(21.21).toPrecision(5)
``````

Then we get `“21.210”` .

We can also pass in a number that’s smaller than the number of decimal digits in the number.

Then we get a string with the number formatted into exponential notation.

For instance, we can write:

``````(21.21).toPrecision(1)
``````

And we get `“2e+1”` .

### Converting a Number to a String

The `toString` method converts a number to a string.

The argument it takes is the radix.

For instance, if we want to convert the decimal number 10 to binary, we can write:

``````(10).toString(2)
``````

Then it returns `“1010"` .

### Parsing a String into an Integer

We can parse a string into an integer with the `parseInt` method.

For instance, we can write:

``````Number.parseInt('10.00')
``````

and we get back 10.

It also takes a second argument with the radix.

So if we want to convert it to a given base, we can do that by writing:

``````Number.parseInt('16', 16)
``````

Then we get 22 since we converted `'16'` to a base 16 number.

### Parsing a String into a Floating Point Number

There’s the `Number.parseFloat` method to convert a string into a floating-point number.

For instance, we can write:

``````Number.parseFloat('10.00')
``````

and get 10.

It can also convert a string to a number if it starts with a number by removing the non-numerical parts and converting the rest to a number.

For example, we can write:

``````Number.parseFloat('36 bottles')
``````

Then we get 36.

### Check if a Number is Within a Safe Range

In JavaScript, a number is considered to be safe if it’s between `-2 ** 53` and `2 ** 53` .

To check that, we can use the `Number.isSafeInteger` method.

For instance, we can write:

``````Number.isSafeInteger(2 ** 53)
``````

which returns `true` , and:

``````Number.isSafeInteger(2 ** 53 + 1)
``````

which is `false` .

### Checking if a Value is NaN

Checking for `NaN` is tricky.

Therefore, we should use the `Number.isNaN` to do it since we can’t use `===` to do the comparison.

For instance, we can write:

``````Number.isNaN(NaN)
``````

and that would return `true` .

Also:

``````Number.isNaN('foo' / 'bar')
``````

returns `true` .

### Check if a value is an Integer

The `isInteger` method lets us check if a value is an integer.

We can use it by writing:

``````Number.isInteger(1)
``````

which returns `true` , or:

``````Number.isInteger(0.2)
``````

which returns `false` .

### Trimming the beginning of a String

We can remove whitespace from the beginning of a string with the `trimStart` method.

For instance, we can write:

``````'   foo'.trimStart()
``````

Then it returns `“foo”` .

### Trimming the End of a String

There’s also the `trimEnd` method to remove whitespace from the end of a string.

For example, we write:

``````'foo   '.trimStart()
``````

Then it returns `“foo”` .

### Trimming Both Ends of a String

The `trim` method will remove whitespace from both ends of a string.

For instance, we can write:

``````'   foo   '.trim()
``````

Then it returns `'foo'` .

### Conclusion

There are various ways to parse and check numbers.

Also, JavaScript strings have methods to remove whitespaces.

## By John Au-Yeung

Web developer specializing in React, Vue, and front end development.