1.通过值查找属性名

const findKey = (value, obj, compare = (a, b) => a === b) => {
  return Object.keys(obj).find(k => compare(obj[k], value));
};

2.数字保留小数

const toFixed = (value, number) => {
  if (!value) value = 0;
  return parseFloat(value.toFixed(number));
};

3.