I make a Calculator in JavaScript

Question

I make a Calculator in Java script but the code dosnt going:

var y = 30
var x = 10
var resu = 2
var op = prompt("Schreibe den Operator");
if (op = "+") {
resu = (x + y);
alert("Das ergebnis ist:" + resu);
} else {
if (op = "-") {
resu = (y - x);
alert("Das ergebnis ist: " + resu);
}
} else {
if (op = ""){
alert("Sie haben keinen gültigen Operator angegeben");
}
}

Answer 1

if (op == "+") ……

Answer 2

var y = 30;
var x = 10;
var resu = 2;
var op = prompt("Schreibe den Operator");
if (op == "+") {
resu = (x + y);
alert("Das ergebnis ist:" + resu);
} else {
if (op == "-") {
resu = (y - x);
alert("Das ergebnis ist: " + resu);
}
} else {
if (op == ""){
alert("Sie haben keinen gültigen Operator angegeben");
}
}

Answer 3

works?

Answer 4

Complement to @ValentinHacker:

Replace the single equal sign by a paired one (==): one equal sign is the affectation operator, since two are comparison operator ^^

Answer 5

@Finnlukas:
Why don't you answer to @Filip?...

Well, for your pleasure, your code corrected, so it's work:

var y = 30;
var x = 10;
var resu = 2;
var op = prompt("Schreibe den Operator");
if (op == "+") {
resu = (x + y);
alert("Das ergebnis ist:" + resu);
}
else if (op == "-") {
resu = (y - x);
alert("Das ergebnis ist: " + resu);
}
else if (op == "") {
alert("Sie haben keinen gültigen Operator angegeben");
}

I've just removed ( and reformat a little ) the brackets of your 'else' statement... If you enclose the 'if' statement, the next ( second ) else statement will attempt to be linked to the first, instead of the second 'if':

if (false) {
/* code not executed */
}
else { /* block executed */
if (false) {
/* code not executed */
}
}
else {
/* what else? this is the error displayed by javascript interpretor */
}

So, if you don't remove the brackets ( if the 'else' block contains more than one instruction -- 'if' and its block is once instruction ), you need to close the first 'else' block after the second, which applied to the second if:

if (false) {
/* code not executed */
}
else { /* block executed */
if (false) {
/* code not executed */
}
else {
/* what else? this is the error displayed by javascript interpretor */
}
}

Notice the indentation changes: this help greatly to see mistake ;)

[ EDIT ]
@Kamil is right ^^

( but it was working without for me, in code playground, on app' / tablet android Oo )

Answer 6

Thanks for the Code

Answer 7

don't forget the semi colons in the first 3 lines

Answer 8

Thanks for good anwser