How to convert number to string

JavaScript Convert Number to String

Introduction

Managing data is one of the fundamental concepts of programming. Because of this, JavaScript offers plenty of tools to parse various data types, allowing you to easily interchange the format of data. Particularly, I’ll be covering how to convert a Number to a String in this article. In another article I’ll also be covering how to convert a String to an Number in JavaScript.

Comparing Data Types in JavaScript

JavaScript is a versatile language, which lets the programmer control how strict the data typing will be.

There are two main ways of comparing equality between two data structures/elements, two equal signs ( == ) or three equal signs ( === ).

When using two equal signs, the variables are compared only by its content. For this example, the ternary operator will be used, which is an if statement shortcut.

On the other hand, when using three equal signs, the variables are compared by content and by data type:

Converting Number to String

There are some built-in methods in JavaScript that provide conversion from an number data type to a String, which only differ in performance and readability.

.toString()

String()

The String() method creates a primitive String type for the number that is passed to it:

The main difference here is that the String object does not do any base conversions like Number.toString() does.

Template Strings

With the introduction of template strings in ES6, injecting a number inside a String is a valid way of parsing an Integer or Float data type:

Concatenating an Empty String

Last, but not least, there is a nifty way of creating a String from a number. Arguably one of the most performance-driven way of doing so, even though some readability is compromised:

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Depending on the browser this code runs on, it may be the fastest way of converting a number to a string. But also keep in mind that this method may not always return the desired string. For example:

Conclusion

There are many valid ways of manipulating data. It is up to the programmer to decide which one they prefer, choosing performance over readability or a balance between the two.

For more information, you can visit the following:

JavaScript Number to String – How to Use toString to Convert an Int into a String

The toString() method is a built-in method of the JavaScript Number object that allows you to convert any number type value into its string type representation.

How to Use the toString Method in JavaScript

To use the toString() method, you simply need to call the method on a number value. The following example shows how to convert the number value 24 into its string representation. Notice how the value of the str variable is enclosed in double quotation marks:

Convert a number to string with toString() method

You can also call the toString() method immediately on a number value, but you need to add parentheses () to wrap the value or JavaScript will respond with an Invalid or unexpected token error.

The toString() method can also convert floating and negative numbers as shown below:

Convert any type of numbers with toString() method

Finally, the toString() method also accepts the radix or base parameter. The radix allows you to convert a number from the decimal number system (base 10) to a string representing the number in other number systems.

Valid number systems for conversion include:

Converting decimal number to binary number with toString() method

The decimal number 5 from the code above is converted to its binary number equivalent of 101 and then converted to a string.

How to Use Other Data Types with the toString() Method

Aside from converting the number type, the toString() method is also available for converting other data types into their string representations.

For example, you can convert an array type into its string representation as follows:

Convert an array to string with toString() method

Or a boolean type to string as shown below:

But I think you will most often use the toString() method to convert a number to a string instead of the others. That’s what I usually do, too 🙂

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How to convert a number to string and vice versa in C++

Since this question gets asked about every week, this FAQ might help a lot of users.

How to convert an integer to a string in C++

how to convert a string into an integer in C++

how to convert a floating-point number to a string in C++

how to convert a string to a floating-point number in C++

5 Answers 5

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Update for C++11

As of the C++11 standard, string-to-number conversion and vice-versa are built in into the standard library. All the following functions are present in (as per paragraph 21.5).

string to numeric

Each of these take a string as input and will try to convert it to a number. If no valid number could be constructed, for example because there is no numeric data or the number is out-of-range for the type, an exception is thrown ( std::invalid_argument or std::out_of_range ).

Finally, the integral types allow to specify a base, for digits larger than 9, the alphabet is assumed ( a=10 until z=35 ). You can find more information about the exact formatting that can parsed here for floating-point numbers, signed integers and unsigned integers.

Finally, for each function there is also an overload that accepts a std::wstring as it’s first parameter.

numeric to string

These are more straightforward, you pass the appropriate numeric type and you get a string back. For formatting options you should go back to the C++03 stringsream option and use stream manipulators, as explained in an other answer here.

As noted in the comments these functions fall back to a default mantissa precision that is likely not the maximum precision. If more precision is required for your application it’s also best to go back to other string formatting procedures.

How to convert a number to a string in C++03

Use string streams

Note that you can use string streams also to convert floating-point numbers to string, and also to format the string as you wish, just like with cout

Use boost lexical cast. If you are not familiar with boost, it is a good idea to start with a small library like this lexical_cast. To download and install boost and its documentation go here. Although boost isn’t in C++ standard many libraries of boost get standardized eventually and boost is widely considered of the best C++ libraries.

Lexical cast uses streams underneath, so basically this option is the same as the previous one, just less verbose.

How to convert a string to a number in C++03

The most lightweight option, inherited from C, is the functions atoi (for integers (alphabetical to integer)) and atof (for floating-point values (alphabetical to float)). These functions take a C-style string as an argument ( const char * ) and therefore their usage may be considered a not exactly good C++ practice. cplusplus.com has easy-to-understand documentation on both atoi and atof including how they behave in case of bad input. However the link contains an error in that according to the standard if the input number is too large to fit in the target type, the behavior is undefined.

In case of a bad input, lexical_cast throws an exception of type boost::bad_lexical_cast

5 ways to convert a number to string in JavaScript

In JavaScript, you can represent a number as type number (ex. 12), or as a type string (ex. ’12’).But both are not same. At times while coding we might have to convert the data from one type to other and there are many ways to do that. I would like to list few of the methods I know of data conversion from number to string.

There is a default string method that converts the data to string. The toString() method returns the value of a String object.

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2. Using String()

The String() method creates a primitive String type for the number that is passed to it.

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3. Concatenating the Empty String

Adding empty string to the number value will convert the data to string is one of the simplest way to do the job. It is also considered to be faster than the above two when it comes to performance.

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4. Template Strings

With the introduction of template strings in ES6, injecting a number inside a String is a valid way of parsing an Integer or Float data type. This is the fastest way to convert the number to string.

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5. Using toFixed() method

This is the least known method. But it can be little tricky with the decimal numbers.

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Here is the comparison of the methods when it comes to the performance. Comment below if you know more ways.
Thank you

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How to convert an int to string in C?

How do you convert an int (integer) to a string? I’m trying to make a function that converts the data of a struct into a string to save it in a file.

11 Answers 11

Trending sort

Trending sort is based off of the default sorting method — by highest score — but it boosts votes that have happened recently, helping to surface more up-to-date answers.

It falls back to sorting by highest score if no posts are trending.

Switch to Trending sort

You can use sprintf to do it, or maybe snprintf if you have it:

Where the number of characters (plus terminating char) in the str can be calculated using:

EDIT: As pointed out in the comment, itoa() is not a standard, so better use sprintf() approach suggested in the rivaling answer!

You can use itoa() function to convert your integer value to a string.

Here is an example:

If you want to output your structure into a file there is no need to convert any value beforehand. You can just use the printf format specification to indicate how to output your values and use any of the operators from printf family to output your data.

The short answer is:

The longer is: first you need to find out sufficient size. snprintf tells you length if you call it with NULL, 0 as first parameters:

Allocate one character more for null-terminator.

After having looked at various versions of itoa for gcc, the most flexible version I have found that is capable of handling conversions to binary, decimal and hexadecimal, both positive and negative is the fourth version found at http://www.strudel.org.uk/itoa/. While sprintf / snprintf have advantages, they will not handle negative numbers for anything other than decimal conversion. Since the link above is either off-line or no longer active, I’ve included their 4th version below:

This is old but here’s another way.

Converting anything to a string should either 1) allocate the resultant string or 2) pass in a char * destination and size. Sample code below:

Method 1: Returns NULL on out-of-memory.

Method 2: It returns NULL if the buffer was too small.

[Edit] as request by @Alter Mann

(CHAR_BIT*sizeof(int_type)-1)*10/33+3 is at least the maximum number of char needed to encode the some signed integer type as a string consisting of an optional negative sign, digits, and a null character..