What's the Most Efficient Way to Check Variable Equality Against Multiple Values in JavaScript?

Efficient Variable Equality Check against Multiple Values

When comparing a variable to multiple predetermined values, a straightforward method is to use a series of logical OR operators:

if( foo == 1 || foo == 3 || foo == 12 ) {
    // ...
}

Although this approach works, it can become cumbersome for a large number of values. An alternative solution is to utilize an object as follows:

if( foo in {1: 1, 3: 1, 12: 1} ) {
    // ...
}

However, this method also introduces redundancy by requiring the repetition of values within the object.

Fortunately, in ECMA2016, a more elegant and performant solution is available: the includes method. This method allows you to efficiently check if a value is contained within an array:

if([1,3,12].includes(foo)) {
    // ...
}

This syntax provides a concise and efficient way to perform equality checks against multiple values. Supported by all major browsers, it is the recommended approach for such comparisons.

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