nodejs convert numbers

Node.js is a popular JavaScript runtime environment commonly used to create efficient web applications. Numbers are a common data type in Node.js. This article explains how to convert a string into a number.

JavaScript supports 7 data types: string (string), number (number), boolean (Boolean value), object (object), function (function), symbol (symbol) and undefined (undefined) . Among them, strings and numbers are the most common types. And Node.js is based on JavaScript, so it also supports these two data types.

The number types in JavaScript are divided into two types: integers and floating point numbers. Integers represent numbers without decimal parts, such as 1, 2, 3, etc. Floating point numbers represent numbers with a decimal part, such as 1.5, 2.75, etc.

In Node.js, we can use the parseInt() and parseFloat() functions to convert strings to numbers.

The parseInt() function converts a string into an integer. Its syntax is as follows:

parseInt(string, radix)

where string is the string to be converted, radix represents the base number to be used. If you do not specify a base number, decimal is used by default.

For example, the following code converts the string "123" into an integer type number:

let num1 = parseInt("123");
console.log(num1); // 123

And if the string "101" is regarded as a binary number, it can be written as follows:

let num2 = parseInt("101", 2);
console.log(num2); // 5

The parseFloat() function converts a string to a floating point number. Its syntax is as follows:

parseFloat(string)

where string is the string to be converted. For example, the following code converts the string "3.14" to a floating-point number:

let num3 = parseFloat("3.14");
console.log(num3); // 3.14

It should be noted that when using the parseFloat() function, if the string does not start with a number, NaN will be returned (Not a Number).

For example, in the following code, since the first character of the string is a letter, NaN will be returned:

let num4 = parseFloat("a3.14");
console.log(num4); // NaN

In addition to the parseInt() and parseFloat() functions, we can also use Number() function converts string to numeric type.

The Number() function has the following three uses:

1. Convert the string to a numeric type:

let num5 = Number("123");
console.log(num5); // 123

If the string cannot be converted to Number, NaN will be returned.

let num6 = Number("ABC");
console.log(num6); // NaN

2. Convert Boolean value to numeric type:

let num7 = Number(true);
let num8 = Number(false);
console.log(num7); // 1
console.log(num8); // 0

true will be converted to 1, and false will be converted to 0.

3. Convert other data types to numeric types:

let num9 = Number(null);
let num10 = Number(undefined);
console.log(num9); // 0
console.log(num10); // NaN

null will be converted to 0, and undefined will be converted to NaN.

In Node.js, the above three methods can be used to convert strings to numeric types.

To summarize, no matter what the scenario, converting a string to a numeric type is a very common operation. In Node.js, we can use the above methods to achieve this operation. It is necessary to choose the appropriate method according to the specific situation.

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