How to determine whether numbers are equal in js-JS Tutorial-php.cn

How to determine whether numbers are equal in js

藏色散人

Release： 2023-01-03 09:26:41

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JS method to determine the equality of numbers: first create an HTML sample file; then add a script tag; finally determine the number through "document.getElementById("demo").innerHTML = (x == 8);" Whether they are equal or not is enough.

How to determine whether numbers are equal in js

The operating environment of this article: Windows 7 system, JavaScript version 1.8.5, Dell G3 computer.

In JavaScript, you can directly use the comparison operator "==" to compare whether two numbers are equal. When comparing numbers with numbers, you cannot put 0 in front of it because 0 represents an octal number in the program.

1. JavaScript determines whether the numbers are equal.

console.log(012==12);  //false
console.log(012==10);  // true
console.log(099==99);  //true 这种情况是因为八进制中不可能出现9，所以看成一个十进制
console.log(09==9);    //true 同上

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Example:

<!DOCTYPE html>
<html>
<body>
<h1>JavaScript比较</h1>
<p>把 5 赋值给 x，然后显示比较 (x == 8) 的值：</p>
<p id="demo"></p>
<script>
var x = 5;
document.getElementById("demo").innerHTML = (x == 8);
</script>
</body>
</html>

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Running results:

How to determine whether numbers are equal in js

##[Recommended video tutorial:

js basic tutorial]

JavaScript compares whether two values are equal:

2. Under normal circumstances, convert both sides into number type data as much as possible, and then compare, rather than converting to Boolean type

console.log(true==2);   // false

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If both sides are converted to Boolean type and then compared, then true==true and false will not be returned, so it proves that it is not both sides that are converted to Boolean type and then compared! ! It should be that both sides are converted to number type, 1==2, and false

console.log(true==1);   // true

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3, underfined, null, 0, NaN, and "" will all become false when converted to Boolean values, then How does it perform in "=="?

①Underfined and null

Undefined and null return false when compared with any meaningful value. Null and undefined are equal to other numbers in the operation No type conversion is performed, but null==undefined

console.log(null==undefined);  //true  
console.log(null===undefined);  //false ===: 全等：不仅比较值是否相等，数据类型要相同
console.log(null==0);          // false
console.log(undefined==1);     //false
console.log(null==false);       // false
console.log(undefined=="");     // false

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