# How to convert a string representation of a number into a integer with javascript ?

Published: March 03, 2022

Updated: December 09, 2022

Tags: Javascript;

Examples of how to convert a string representation of a number into a integer with javascript :

### Convert a string into an integer

Let's consider the following variable

````var s = '42'`
```

The variable type can be checked using typeof

````console.log( typeof s );`
```

gives here

````string`
```

To convert the above string into a integer, a solution is to use parseInt()

````var i = parseInt(s)`

`console.log( i );`
```

gives

````42`
```

and now if we check the type

````console.log( typeof i );`
```

it returns:

````number`
```

#### if s = '3.1415'

if the string is a represenation of a float

````var s = '3.1415'`
`var i = parseInt(s)`
`console.log( i );`
```

it gives

````3`
```

#### if s = '301 984 2472'

If the string contains number separated by spaces:

````var s = '301 984 2472'`
`var i = parseInt(s)`
`console.log( i );`
```

its returns the first number

````301`
```

#### if s = 'I am 42''

If the string starts with a letter:

````var s = 'I am 42'`
`var i = parseInt(s)`
`console.log( i );`
```

it gives

````NaN`
```

#### if s = '42 is the answer!''

However if the string starts with a number

````var s = '42 is the answer!'`
`var i = parseInt(s)`
`console.log( i );`
```

it gives

````42`
```

### Comparing a string with a integer

Note:

````var s = '42'`
`var i = parseInt(s)`

`console.log( i == s );`
```

gives

````true`
```

while

````console.log( i === s );`
```

gives

````false`
```