howitworks-array-2.js

miniFc.array = (itemGenerator) => {
    return {
        generate(mrng) {
            const size = mrng.next(0, 10);
            const content = [];
            for (let index = 0 ; index !== size ; ++index) {
                content.push(itemGenerator.generate(mrng));
            }
            return content;
        },
        *shrink(value) {
            // No shrink on empty arrays
            if (value.length === 0) {
                return;
            }
            // Step 1. Shrink on size first by keeping last items
            let removedSize = Math.floor(value.length / 2);
            while (removedSize > 0) {
                yield value.slice(removedSize);
                removedSize = Math.floor(removedSize / 2);
            }
            // Step 2. Shrink the first item alone
            for (const shrunkItemValue of itemGenerator.shrink(value[0])) {
                yield [shrunkItemValue, ...value.slice(1)];
            }
            // Step 3. Keep first item untouched
            for (const shrunkValue of this.shrink(value.slice(1))) {
                yield [value[0], ...shrunkValue];
            }
        }
    }
}
// You can check the output by calling:
// > [...miniFc.array(miniFc.integer(0, 100)).shrink([4, 1, 2, 1, 3])]