How to Check if a Value Exists in a Map in JavaScript

How to Check if a Value Exists in a Map in JavaScript ?

Answer

To check if a value exists in a map in JavaScript, you need to iterate through the map's values and compare each value. This approach helps determine if a specific value is present in the map.

✐ Examples

1 Checking if a Value Exists Using Loop

We can check if a value exists in a map in JavaScript by iterating through the map's values and comparing each value to the specified value.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We declare a boolean variable valueExists and initialize it to false. This variable will be used to indicate if the value is found in the map.
We use a for...of loop to iterate through each value in the map using the values() method. Inside the loop, we compare the current value with the specified value.
If the value matches the specified value, we set valueExists to true and break the loop.
We print the result to the console using the console.log function.

JavaScript Program

const myMap = new Map([
    ['one', 1],
    ['two', 2],
    ['three', 3]
]);

// Check if a value exists using loop
let valueExists = false;
for (const value of myMap.values()) {
    if (value === 2) {
        valueExists = true;
        break;
    }
}

// Print the result
console.log(`Does value 2 exist? ${valueExists}`);

Output

Does value 2 exist? true

2 Checking if a Value Does Not Exist Using Loop

We can check if a value does not exist in a map in JavaScript by iterating through the map's values and comparing each value to the specified value.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We declare a boolean variable valueExists and initialize it to false. This variable will be used to indicate if the value is found in the map.
We use a for...of loop to iterate through each value in the map using the values() method. Inside the loop, we compare the current value with the specified value.
If the value matches the specified value, we set valueExists to true and break the loop.
We print the result to the console using the console.log function.

JavaScript Program

const myMap = new Map([
    ['one', 1],
    ['two', 2],
    ['three', 3]
]);

// Check if a value does not exist using loop
let valueExists = false;
for (const value of myMap.values()) {
    if (value === 4) {
        valueExists = true;
        break;
    }
}

// Print the result
console.log(`Does value 4 exist? ${valueExists}`);

Output

Does value 4 exist? false

3 Checking Multiple Values Using Loop

We can check if multiple values exist in a map in JavaScript by iterating through the map's values and comparing each value to the specified values.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We declare two boolean variables valueExistsOne and valueExistsFour, and initialize them to false. These variables will be used to indicate if the values are found in the map.
We use a for...of loop to iterate through each value in the map using the values() method. Inside the loop, we compare the current value with the specified values.
If the value matches one of the specified values, we set the corresponding boolean variable to true.
We print the results to the console using the console.log function.

JavaScript Program

const myMap = new Map([
    ['one', 1],
    ['two', 2],
    ['three', 3]
]);

// Check if multiple values exist using loop
let valueExistsOne = false;
let valueExistsFour = false;
for (const value of myMap.values()) {
    if (value === 1) {
        valueExistsOne = true;
    }
    if (value === 4) {
        valueExistsFour = true;
    }
}

// Print the results
console.log(`Does value 1 exist? ${valueExistsOne}`);
console.log(`Does value 4 exist? ${valueExistsFour}`);

Output

Does value 1 exist? true
Does value 4 exist? false

Summary

In this tutorial, we learned How to Check if a Value Exists in a Map in JavaScript language with well detailed examples.

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How to Check if a Value Exists in a Map in JavaScript