![]() If the input is an empty string ( Number('')) then NaN (Not a Number) is returned. '123abc') then parseInt() will return the number from the beginning of the string (e.g. ![]() If the input string begins with a number (e.g. The parseFloat() function accepts a string parameter and converts it to an floating point number (with a decimal point if required), or returns NaN (Not a Number) if the input value doesn't represent a number. The parseInt() function accepts a string parameter and converts it to an integer number, or returns NaN (Not a Number) if the input value doesn't represent a number. The way to check if a value equals NaN is to use the isNan() function. An interesting thing to note is that zero ( 0) is returned for an empty string ( Number('')). The Number() function accepts a string parameter and converts it to an integer or floating point number, or returns NaN (Not a Number) if the input value doesn't represent a number. It is up to the programmer to decide which one they prefer, choosing performance over readability or a balance between the two.This is a quick post to show examples of 7 different ways to convert a string to a number in JavaScript along with the output that each gives for different values. There are many valid ways of manipulating data. Instantiating a primitive data type with the String or Number class wrapper brings performance and memory issues. When using primitive data the object methods should not be used to create them. Number to String let numToStr = new String( 2) // String Using String and Number ObjectsĪnother way of transforming a String to number or a number to String is creating a new String or Number object with the new keyword. The previous two approaches work simply due to the fact that JavaScript tries to assimilate the data-types used in a statement such as addition or multiplication. This approach is arguably the fastest one: let str = '100' While concise and effective, this isn't a very well-known feature of JavaScript, so it's not advised to use since it may make your code not as easy to understand. Unary OperatorĪs with Concatenating an Empty String, there is also a workaround that has better performance but lacks readability. Keep in mind that if you're needing to parse floats then both Math.floor and Math.ceil are probably not good options since they'll always convert the strings to the nearest integer equivalent. Math.ceil(str) // 100 Math.ceil(fltStr) // 101 Math.ceil(nanStr) // NaN The method can accept Strings, also making it a way to convert a String to a number: let str = '100' Very similar to the previous method, Though, this time it returns the nearest integer rounded up. Math.floor(str) // 100 Math.floor(fltStr) // 99 Math.floor(nanStr) // NaN Math.ceil() Surprisingly, this method can also accept Strings, making it yet a way to convert a String to an integer. ParseFloat(str) // 353 parseFloat(fltStr) // 353.21 parseFloat(nanStr) // NaN Math.floor() ![]() ParseInt(str) // 353 parseInt(fltStr) // 353 parseInt(binStr, 2) // 111 (Binary) parseInt(nanStr) // NaN (Not a Number). 0x - If the prefix is 0x, then the radix is 16 (hexadecimal).Īlthough, we can simply add an optional argument to the method call, defining the base: let str = '353'.0 - If the prefix is 0, then the radix is 8 (octal).No prefix - If there isn't a prefix, the radix is 10 (decimal).The base can be defined by adding prefixes to the numbers we want to parse: If a String is multiplied by the primitive number 1, the string will become a number. Unary Operator By adding a + sign before a String, it will be converted into a number if it follows the right format.Math.ceil() can be used to round an integer or floating point number.It returns the nearest integer rounded down. ![]()
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