用javascript写了个base32的编解码函数

const charTable=[
	'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',
	'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',
	'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',
	'Y', 'Z', '2', '3', '4', '5', '6', '7',
	'='
],allowedPeddingCount=[6,4,3,1,0];

function str_split(str,length){
	if(typeof str !== 'string')return [];
	let a=[],i=0;
	length||(length=1);
	do{
		a.push(str.substr(i,length));
		i+=length;
	}while(i<str.length);
	return a;
}

const Base32={
	encode:function(str,padding){
		if(!str)return '';
		let binaryString='';
		for (let i = 0;i<str.length;i++) {
			let bin=str.charCodeAt(i).toString(2);
			binaryString+=('0'.repeat(8-bin.length)+bin);
		}
		let fiveBitBinaryArray=str_split(binaryString,5),base32='';
		for(let i=0;i<fiveBitBinaryArray.length;i++){
			let bin=fiveBitBinaryArray[i];
			base32+=charTable[parseInt(bin+'0'.repeat(5-bin.length),2)];
		}
		let x=binaryString.length%40;
		if (padding && x != 0) {
			if (x == 8)base32+=charTable[32].repeat(6);
			else if(x===16)base32+=charTable[32].repeat(4);
			else if(x===24)base32+=charTable[32].repeat(3);
			else if(x===32)base32+=charTable[32];
		}
		return base32;
	},
	decode:function(str){
		if(!str)return '';
		let paddingMatch=str.match(/\=+$/),
			paddingCharCount=paddingMatch?paddingMatch[0].length:0;
		if(allowedPeddingCount.indexOf(paddingCharCount)<0)return false;
		for (let i=0;i<4;i++){
			if (paddingCharCount===allowedPeddingCount[i] 
				&& str.substr(-(allowedPeddingCount[i]))!=charTable[32].repeat(allowedPeddingCount[i]))
				return false;
		}
		str=str.replace(/\=+$/,'');
		let binaryString = "";
		for (let i=0;i<str.length;i+=8) {
			let x='';
			if (charTable.indexOf(str[i])<0)return false;
			for (let j=0;j<8;j++) {
				let bin=charTable.indexOf(str[i+j]).toString(2);
				x+='0'.repeat(5-bin.length)+bin;
			}
			let eightBits=str_split(x,8);
			for (let z = 0; z < eightBits.length; z++) {
				let y,cd=parseInt(eightBits[z],2,10);
				binaryString+=((y=String.fromCharCode(cd))||cd==48)?y:"";
			}
		}
		return binaryString;
	}
}