node.js string.replace doesn't work?

问题:

var variableABC = "A B C"; 
variableABC.replace('B', 'D') //wanted output: 'A D C'

but 'variableABC' didn't change :

variableABC = 'A B C'

when I want it to be 'A D C'.

回答1:

According to the Javascript standard, String.replace isn't supposed to modify the string itself. It just returns the modified string. You can refer to the Mozilla Developer Network documentation for more info.

You can always just set the string to the modified value:

variableABC = variableABC.replace('B', 'D')

Edit: The code given above is to only replace the first occurrence.

To replace all occurrences, you could do:

 variableABC = variableABC.replace(/B/g, "D");  

To replace all occurrences and ignore casing

 variableABC = variableABC.replace(/B/gi, "D");  

回答2:

Strings are always modelled as immutable (atleast in heigher level languages python/java/javascript/Scala/Objective-C).

So any string operations like concatenation, replacements always returns a new string which contains intended value, whereas the original string will still be same.

回答3:

Isn't string.replace returning a value, rather than modifying the source string?

So if you wanted to modify variableABC, you'd need to do this:

var variableABC = "A B C";

variableABC = variableABC.replace('B', 'D') //output: 'A D C'

回答4:

If you just want to clobber all of the instances of a substring out of a string without using regex you can using:

    var replacestring = "A B B C D"
    const oldstring = "B";
    const newstring = "E";
    while (replacestring.indexOf(oldstring) > -1) {
        replacestring = replacestring.replace(oldstring, newstring);
    }        
    //result: "A E E C D"