在Javascript中将" null“字符串替换为null

var str = "This is a null string";
var replacedStr = str.replace(/null/g, "null");

console.log(replacedStr); // "This is a null string"
console.log(typeof replacedStr); // "string"

var nullStr = replacedStr.replace(/null/g, null);

console.log(nullStr); // "This is a  string"
console.log(typeof nullStr); // "string"
console.log(nullStr === null); // false
console.log(nullStr === "null"); // false
console.log(nullStr === ""); // true