Why String to Number Comparison Works in Javascript
In Javascript, you may encounter code that compares a string coming from an HTML text field with integers, like this:
x >= 1 && x <= 999;
This condition checks if the value x from the text field falls between 1 and 999 (inclusive), and it surprisingly works as expected. However, x is a string, while the condition involves integers. Shouldn't this lead to errors?
The Answer: Operator Coercion
Javascript defines operators like >= and <= to allow for coercion between different data types. Here's how it works:
- Both Operands as Strings: If both operands are strings, a string comparison is performed. For example, "90" > "100" because the comparison is based on character order rather than numeric value.
- One Operand as Non-String: If one of the operands is not a string, the operands are coerced to numbers. Thus, "90" < 100 because the former is coerced to the number 90 before the numeric comparison.
Implications
This coercion behavior can lead to unexpected results, such as:
"90" > "100" because strings are compared. Should You Use parseInt()? Whether to use parseInt() to convert x to an integer before comparison is a matter of preference. Some prefer to rely on implicit coercion, while others prefer explicit conversion for clarity and consistency. Conversion Options If you choose explicit conversion, you have various options beyond parseInt(): Consider the implications and choose the option that best suits your code's needs. The above is the detailed content of Why Does String-to-Number Comparison Work in JavaScript?. For more information, please follow other related articles on the PHP Chinese website!
"90" < 100 because numbers are compared.
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