Check if Variable Doesn't Equal Multiple Values in JS

Check if Variable Doesn't Equal Multiple Values #

To check if a variable is not equal to multiple values:

1. Use the logical and (&&) operator to chain multiple conditions.
2. In each condition, use the strict inequality operator (!==) to check that the variable is not equal to the value.
3. If all conditions pass, the variable is not equal to any of the values.

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const a = 'one';
const b = 'two';
const c = 'three';

if (a !== b && a !== c) {
  console.log('✅ a is not equal to b and c');
} else {
  console.log('⛔️ a is equal to b or c, or both');
}

We used the strict inequality (!==) operator to check if the variable a is not equal to the variables b and c.

The operator returns a boolean result:

• true if the values are not equal
• false if the values are equal

To chain the two conditions we used the logical and (&&) operator.

The if block would only run if both conditions return true.

If the a !== b part of the condition returns false, the a !== c part is not evaluated at all.

For example, in the following if statement, the 10 > 1 condition is never evaluated.

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if (5 > 50 && 10 > 1) {
}

We first check if 5 > 50 and get a value of false, so the && operator short-circuits.

Here are some more examples of using the && (and) operator.

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console.log(true && true); // 👉️ true
console.log(true && false); // 👉️ false
console.log(false && true); // 👉️ false
console.log('abc' && 'hello'); // 👉️ 'hello'
console.log('hello' && ''); // 👉️ ''
console.log('' && 'hello'); // 👉️ ''

The && operator returns the value of one of the operands.

If the first value we pass to it is a falsy value, it returns the first value, otherwise it returns the second.

Falsy values in JavaScript are: undefined, null, NaN, empty string, false and 0.

In our last example, because we used an empty string as the first value and an empty string is falsy, it got returned from the && operator.

In short, if the value to the left is falsy, it gets returned from the && operator. In all other cases the operator returns the value to the right.

Further Reading #

• Check if a Variable is Not NULL in JavaScript
• Check if two Numbers are NOT equal in JavaScript