如何使字符串变异？ JavaScript的

Question

if objects are mutable by default why in this case it dosen't work? How to make mutation value of the key "a" in the object "s"?

 var s = { a: "my string" }; sa[0] = "9"; // mutation console.log(sa); // doesn't work 

Answer 1

Strings in JavaScript are immutable. This means that you cannot modify an existing string, you can only create a new string.

var test = "first string";
test = "new string"; // same variable now refers to a new string

Answer 2

You are trying to change a string in javascript which is immutable.

If you want to change the string. You need to define a function in its prototype chain as

String.prototype.replaceAt=function(index, replacement) {
    return this.substr(0, index) + replacement+ this.substr(index + replacement.length);
}

var hello="Hello World"
hello = hello.replaceAt(2, "!!")) //should display He!!o World

Or you can just assign another value to as, as as = 'Hello World'

Answer 3

You try to mutate a string which not possible, because strings are immutable. You need an assignment of the new value.

Below a fancy style to change a letter at a given position.

 var s = { a: "my string" }; sa = Object.assign(sasplit(''), { 0: "9" }).join(''); console.log(sa); 

Answer 4

You are trying to mutate the string using element accessor, which is not possible. If you apply a 'use strict'; to your script, you'll see that it errors out:

 'use strict'; var s = { a: "my string" }; sa[0] = '9'; // mutation console.log( sa ); // doesn't work 

If you want to replace the character of the string, you'll have to use another mechanism. If you want to see that Objects are mutable, simply do sa = '9' instead and you'll see the value of a has been changed.

 'use strict'; var s = { a: "my string" }; sa = sareplace(/./,'9') console.log(sa);