In JavaScript, there are the following methods to convert strings to numbers: 1. Use the Number() function, which is suitable for simple conversion, but returns NaN for non-numeric characters, and converts empty strings to 0; 2. Use parseInt() and parseFloat(), which is suitable for extracting numeric values with units or decimal parts and parsing them to non-numeric characters; 3. Use the unary plus sign ( ) operator, which is the same as Number() but is more concise in writing; 4. When handling exceptions, you can verify the input legitimacy through isNaN() or regular expression to ensure that the conversion result is valid. Choosing the right method based on input format and requirements is key.

In JavaScript, converting strings to numbers is a common requirement, especially when processing user input or getting data from an interface. It can be achieved directly with some built-in methods, but different scenarios are suitable for different methods. Here are a few practical methods.

Use Number() function

This is one of the easiest and straightforward ways. Number() is a global function that converts strings, boolean values, etc. into numbers.

 Number("123"); // 123
Number("12.3"); // 12.3
Number(""); // 0
Number("123abc"); // NaN

The advantage of this method is that the syntax is concise, but it should be noted that if the string contains non-numeric characters, the result will become NaN (Not a Number). An empty string will be converted to 0 , which may sometimes not meet expectations and requires additional judgment.

Use parseInt() and parseFloat()

These two functions are more suitable for "extracting" integers or floating-point numbers from strings:

• parseInt() : used to parse integers
• parseFloat() : used to parse floating point numbers

 parseInt("123"); // 123
parseInt("123.45"); // 123
parseInt("123px"); // 123
parseFloat("12.3px"); // 12.3

They all start parsing from the beginning of the string until they encounter non-numeric characters. This behavior is very practical if you are dealing with strings with units such as CSS values and size units.

Note: When using parseInt() , it is best to pass in the second parameter (primary), such as parseInt("0123", 10) to avoid analytical differences in different environments.

Use a one-yuan plus sign ( ) operator

Here is a shorter way of writing:

 "123"; // 123
 "12.3"; // 12.3
 ""; // 0
 "abc"; // NaN

It is basically the same as Number() 's behavior, but the writing method is shorter. It is suitable for situations where you want to save a little space in your code, but it is slightly less readable and is not recommended for use in complex logic.

Tips for handling exceptions

In actual development, strings are not always legal in number formats, so it is recommended to make a validity judgment after conversion:

• Check if it is NaN
• You can use isNaN() or typeof to perform verification

For example:

 let str = "123a";
let num = Number(str);
if (!isNaN(num)) {
  // Conversion is successful} else {
  // Handle invalid numbers}

In addition, you can also use regular expressions to verify whether the string format is legal in advance to avoid errors:

 /^-?\d (\.\d )?$/.test(str); // Determine whether it is a digital format

Basically these commonly used methods. Each method has applicable scenarios, and the key depends on how you choose the appropriate method based on the input format and expected results.

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