Function to compare multiple numbers using greater (<) and smaller (>) logic.

compare-nums.js

function compareNums(comparison) {
	if (!comparison) return false;

	const validFormat = /\d+(([<>]=*)\d+)*/;
	const removeSpaces = str => str.replace(/\s/g, '');

	comparison = removeSpaces(comparison);
	const [match] = comparison.match(validFormat);

	if (match.length !== comparison.length) {
		throw new Error('invalid format: the format should match x < y < z...');
	}

	const comparisonParts = comparison.match(/(\d+)|([<>]=*)/g);

	for (let i = 0; i < comparisonParts.length; i += 2) {
		const [
			firstNumber,
			operator,
			secNumber
		] = comparisonParts.slice(i, i + 3);

		if (operator === '>' &&
			!(Number(firstNumber) > Number(secNumber)) ||
			operator === '<' &&
			!(Number(firstNumber) < Number(secNumber)) ||
			operator === '<=' &&
			!(Number(firstNumber) <= Number(secNumber)) ||
			operator === '>=' &&
			!(Number(firstNumber) >= Number(secNumber))
		) {
			return false
		}
	}
	
	return true
}

// Examples of the function
console.log(`1. ${compareNums('10 < 15 < 20')}`); // true
console.log(`2. ${compareNums('10 >= 10')}`); // true
console.log(`3. ${compareNums('5 > 4 > 3 > 2 > 1 > 0')}`); // true
console.log(`4. ${compareNums('10 > 100')}`); // false
console.log(`5. ${compareNums('10 > 10')}`); // false
const variable = 5;
console.log(`6. ${compareNums(`1 < ${variable} < 10`)}`); // true