JSFiddle - React, Tailwind, and code Playground

JavaScript

const ArrayOps = {
	wholeToArnum(n){
		return n.split('').reverse().map(e=>e>>0);
	},
	decToArnum(n){
		//return with level	
		n = n.split('').reverse();
		let decLength = n.indexOf('.');
		n.splice(decLength, 1);
		n = n.map(e=>e>>0);
		while(n[n.length - 1] === 0) n.pop();
		let denom = [1];
		let brake = handBrake(20);
		let loopCount = decLength;
		while(loopCount-- && brake()){
			denom.unshift(0);
		}
		return {numer: n, denom, decLength};
	},
	repDecToArnum(n, precedingDigits = 0){
		let numer = this.wholeToArnum(n);
		let denom = [];
		let ninesCount = numer.length;
		let brake = handBrake(20);
		while(ninesCount-- && brake()){
			denom.unshift(9);
		}
		brake = handBrake(200);
		while(precedingDigits-- && brake()){
			denom.unshift(0);
		}
		return {numer, denom};
	},
	
	add(...nums){
	    nums = nums.filter(e=>{
	       e = e.join('');
	       return !is.zero(e);
	    });
        if(nums.length === 0) return [0];
        
		function compressor(arnum){
			compress = false;
			for(let i = 0; i < arnum.length; i++){
				let curr = arnum[i] || 0;
				if(curr >= 10){
					let next = arnum[i+1] || 0;
					next += drop(curr/10);
					curr %= 10;
					arnum[i] = curr;
					arnum[i+1] = next;
				}
				
			}
		}
		let compress = false;
		let drop = Math.floor;
		let COMP_POINT = drop(Number.MAX_SAFE_INTEGER / 100);
        let sum = nums.shift();
	    while(nums.length > 0){
	        let N = nums.shift();
	        N.forEach((e,i)=>{
	        	let s = sum[i] || 0;
	        	let temp = s + e;
	        	if(temp > COMP_POINT) compress = true;
	        	sum[i] = temp;
	        });
	        if(compress) compressor(sum);
	    }
	    compressor(sum);
	    return sum;
	},
	subtract(minuend, ...subtrahends){
		let sub = this.add(...subtrahends);
		minuend.forEach((e,i,arr)=>{
			let s = sub[i] || 0;
			let diff = e - s;
			if(diff < 0){
				diff += 10;
				arr[i+1]--;
			}
			arr[i] = diff;
		});
		let lastDigit = minuend[minuend.length - 1];
		if(lastDigit < 0 ||...