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In JavaScript, conditions can be used to filter and map arrays.

Filter:

The filter() method creates a new array with all elements that pass the test implemented by the provided function. The provided function takes in the current element being processed and returns a boolean value indicating whether the element should be included in the new array.

Here's an example:

const numbers = [1, 2, 3, 4, 5];

const filteredNumbers = numbers.filter(function(number) {
    return number > 2;
});

console.log(filteredNumbers); // Output: [3, 4, 5]

In this example, the filter() method is used to create a new array called filteredNumbers that contains only the elements of the original numbers array that are greater than 2.

Map:

The map() method creates a new array with the results of calling a provided function on every element in the calling array. The provided function takes in the current element being processed and returns a new value for that element.

Here's an example:

const numbers = [1, 2, 3, 4, 5];

const doubledNumbers = numbers.map(function(number) {
    return number * 2;
});

console.log(doubledNumbers); // Output: [2, 4, 6, 8, 10]

In this example, the map() method is used to create a new array called doubledNumbers where each element of the original numbers array is multiplied by 2.