When using the if-else structure, the following points should be paid attention to: 1. The order of condition judgment must be reasonable, and conditions with high priority should be placed in front to ensure the correct logic; 2. Avoid too deep nesting, and keep the code concise by returning in advance or splitting functions; 3. Else branches are not necessary and can be omitted when there is no processing; 4. Use && and || to simplify the combination of multiple conditions and improve the readability of the code. Following these methods can make the judgment of conditions clearer and more efficient.
When writing code, if-else if-else is one of the most commonly used conditional judgment structures. It allows you to execute different code blocks according to different situations. If used properly, the logic can be clear and the control process will be more flexible; if used poorly, it will be easy to be confused and difficult to understand.
Below are some practical methods and suggestions to help you use if-else if-else more clearly and effectively.
Think about the order of judgment first
if-else if-else is in order. Once a certain condition is met, the following will not be viewed again. So the order is very important.
For example, you wrote a procedure to judge grades:
if (score >= 90) {
grade = 'A';
} else if (score >= 80) {
grade = 'B';
} else if (score >= 70) {
grade = 'C';
} else {
grade = 'D';
}In this example, the order of judgment is from high to low, first check whether it is A, then B, and so on. If you start judging from low scores in turn, the result will be wrong.
Small suggestions:
- Put conditions with high priority first.
- If multiple conditions may be valid at the same time, make sure you figure out which branch you should go to.
Don't nest too deeply, keep it simple
Sometimes, in order to deal with complex logic, many layers of nested if will be written, which will not only make you tired, but also have a headache when others read it.
For example:
if (user.isLoggedIn) {
if (user.isAdmin) {
// do something
} else {
// another thing
}
} else {
// redirect to login
}Although it is not complicated, you can organize the structure a little, such as returning in advance or splitting it into functions.
Optimization ideas:
- When you encounter more than three nested layers, consider whether it can be split into multiple judgments or functions.
- Some languages ??support similar writing methods
guard(such as Swift), and you can also refer to the style of exiting early.
else is not necessary, don't force it
Many people think that each if needs to be equipped with an else , but it is not. Many times, it is clearer without else .
for example:
if (temperature > 30) {
console.log("It's hot outside.");
}
// no else needed hereAt this time, I just want to remind you of the high temperature weather, and there is no need to deal with the situation that is "not high temperature".
Common misunderstandings:
- Forced writing
else { return null; }is actually meaningless. - It is for granted to think that "every situation must be handled", but sometimes doing nothing is the right way to do it.
Combining multiple conditions with && and || simplification
Sometimes you will encounter multiple conditions combinations, such as:
if (age >= 18 && isCitizen) {
// eligible to vote
} In this case, using logical operators well can save a lot of else if .
There is another situation where multiple parallel conditions can be || to merge and judge:
if (role === 'admin' || role === 'moderator') {
// has permission
} This is more intuitive than writing two if to make a separate judgment.
Basically that's it. if-else if-else is simple, it requires a little logical thinking and structural awareness when used well. When you first write, pay more attention to the order and structure, and it will be much easier to read later.
The above is the detailed content of How to use if-else if-else?. For more information, please follow other related articles on the PHP Chinese website!
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