false == ''在js中为何判断为true

当用==操作符将false对象和其他对象进行比较的时候

　　只有0和空字符串、空数组等于false；

　　undefined和null对象并不等于false对象，而null和undefined是相等的。

let completed = false;

console.log(completed == 0);
console.log(completed == '');
console.log(completed == []);
console.log(completed == null);
console.log(completed == undefined);
console.log(null == undefined);