How to use if conditional statement in JavaScript

if in How to use if conditional statement in How to use if conditional statement in How to use if conditional statement in JavaScript can implement conditional branches, which are conditional statements. Therefore, the following article will introduce to you the usage of if conditional statements in How to use if conditional statement in How to use if conditional statement in How to use if conditional statement in JavaScript. Let’s take a look at the specific content.

Let’s first take a look at the syntax of the conditional branch (if statement) statement

if（条件）{
条件为真时执行
}

in ( ). If the condition is true, the processing in {} will be executed.

By the way, consistent conditions are called "true", and inconsistent conditions are called "false".

If you want to add "false" to the if statement, you need to add the code as follows

if（条件）{
条件为真时执行
} else {
条件为假时执行
}

If the condition is applicable, use if processing, if not, use else processing.

Specific example

Use scores to judge

If it is 80 points or more (including 80 points), then congratulations! Passed!

If the score is less than 80, you are not qualified! Work harder next time!

First, let us assume that the score is obtained using variables as follows (set to 90 points here).

The code is as follows

<script>
var score = 90;
if (score >= 80) {
document.write("恭喜你！通过了！") ;
}
</script>

Because the score is higher than 80 points, the running results are as follows

Let’s look at a piece of code again

<script>
var score = 90;
if (score >= 80) {
document.write("恭喜你！通过了！");
} else {
document.write("不合格！下次努力！");
}
</script>

Although this code adds else, since the score is still higher than 80, the result is still "Congratulations! Passed!"

Let's compare the scores Set to 60

<script>
var score = 60;
if (score >= 80) {
document.write("恭喜你！通过了！");
} else {
document.write("不合格！下次努力！");
}
</script

The running results are as follows

Multiple conditional branch statements (else if)

When using conditional statements, you can use multiple conditions to branch. At this time, the else if statement is used.

The else if statement in the conditional statement is as follows

<script>
if (条件) {
条件为真时执行
} else if (条件2) {
条件2为真时执行
}
else {
条件为假时执行
}
</script>

Let’s look at a specific example

<script>
var score = 60;
if (score >= 80) {
document.write("恭喜你！通过了！");
} else if (score >= 70) {
document.write("不合格！加油！");
}
else  {
document.write("不合格！下次努力！");
}
</script>

The running results are as follows

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