20 web3合约中token的单位与wei的关系
PancakeSwap Token (Cake) Token Tracker | BscScan
比如cake的合约，从合约中取得的余额要通过fromWei 或者toWei来换算， 也就是10^18
但是我发现某些代币，换算单位却是10^6，比如这里有个token叫DAR，合约地址是下面这个 Dalarnia (DAR) Token Tracker | BscScan
这种用什么函数来转换呢？ 比如我要转账 send=20.123456，如果直接用 send*10**6，那么这个结果还是float，不能直接丢给transfer函数。 虽然可以用math.floor来处理，我猜想应该是有对应的函数的，但是看文档没有找到。
最佳答案 2021-11-22 09:05
使用 ethers.js 的话，有相应的函数：
ethers.utils.parseUnits() ethers.utils.formatUnits()
可以参考文档：工具包 — ethers.js 中文文档
当然也可以自己实现：
var BN = require('bn.js');
const unitMap = {
'0': '1', // eslint-disable-line
'1': '10', // eslint-disable-line
'2': '100', // eslint-disable-line
'3': '1000', // eslint-disable-line
'4': '10000', // eslint-disable-line
'5': '100000', // eslint-disable-line
'6': '1000000', // eslint-disable-line
'7': '10000000', // eslint-disable-line
'8': '100000000', // eslint-disable-line
'9': '1000000000', // eslint-disable-line
'10': '10000000000', // eslint-disable-line
'11': '100000000000', // eslint-disable-line
'12': '1000000000000', // eslint-disable-line
'13': '10000000000000', // eslint-disable-line
'14': '100000000000000', // eslint-disable-line
'15': '1000000000000000', // eslint-disable-line
'16': '10000000000000000', // eslint-disable-line
'17': '100000000000000000', // eslint-disable-line
'18': '1000000000000000000' // eslint-disable-line
};// 转化为按可视单位位数显示
export function fromDec(weiInput, decimal) {
var wei = new BN(weiInput); // eslint-disable-line
const base = new BN(unitMap[decimal], 10);
const baseLength = unitMap[decimal].length - 1 || 1;
var fraction = wei.mod(base).toString(10); // eslint-disable-line
while (fraction.length < baseLength) {
fraction = `0${fraction}`;
}
fraction = fraction.match(/^([0-9]*[1-9]|0)(0*)/)[1];
var whole = wei.div(base).toString(10); // eslint-disable-line
var value = `${whole}${fraction == '0' ? '' : `.${fraction}`}`; // eslint-disable-line
return value;
}
// 转化为按decimal 位数显示
export function toDec(etherInput, decimal) {
var ether = String(etherInput); // eslint-disable-line
const base = new BN(unitMap[decimal], 10);
const baseLength = unitMap[decimal].length - 1 || 1;
// Split it into a whole and fractional part
var comps = ether.split('.'); // eslint-disable-line
if (comps.length > 2) { throw new Error(`[ethjs-unit] while converting number ${etherInput} to wei, too many decimal points`); }
var whole = comps[0], fraction = comps[1]; // eslint-disable-line
if (!whole) { whole = '0'; }
if (!fraction) { fraction = '0'; }
if (fraction.length > baseLength) { throw new Error(`[ethjs-unit] while converting number ${etherInput} to wei, too many decimal places`); }
while (fraction.length < baseLength) {
fraction += '0';
}
whole = new BN(whole);
fraction = new BN(fraction);
var wei = (whole.mul(base)).add(fraction); // eslint-disable-line
return new BN(wei.toString(10), 10).toString();
}
