Call break in nested if statements
JavascriptJavascript Problem Overview
I have the following situation:
IF condition THEN
IF condition THEN
sequence 1
ELSE
break //?
ENDIF
ELSE
sequence 3
ENDIF
What is the result of the break statement? Does it break the outer if statement? Because this is what I actually need.
Javascript Solutions
Solution 1 - Javascript
If you label the if statement you can use break.
breakme: if (condition) {
// Do stuff
if (condition2){
// do stuff
} else {
break breakme;
}
// Do more stuff
}
You can even label and break plain blocks.
breakme: {
// Do stuff
if (condition){
// do stuff
} else {
break breakme;
}
// Do more stuff
}
It's not a commonly used pattern though, so might confuse people and possibly won't be optimised by compliers. It might be better to use a function and return, or better arrange the conditions.
( function() {
// Do stuff
if ( condition1 ) {
// Do stuff
} else {
return;
}
// Do other stuff
}() );
Solution 2 - Javascript
no it doesnt. break is for loops, not ifs.
nested if statements are just terrible. If you can avoid them, avoid them. Can you rewrite your code to be something like
if (c1 && c2) {
//sequence 1
} else if (c3 && c2) {
// sequence 3
}
that way you don't need any control logic to 'break out' of the loop.
Solution 3 - Javascript
In the most languages, break does only cancel loops like for, while etc.
Solution 4 - Javascript
But there is switch-case :)
switch (true) {
case true:
console.log("Yes, its ture :) Break from the switch-case");
break;
case false:
console.log("Nope, but if the condition was set to false this would be used and then break");
break;
default:
console.log("If all else fails");
break;
}
Solution 5 - Javascript
To make multiple checking statements more readable (and avoid nested ifs):
var tmp = 'Test[[email protected]]';
var posStartEmail = undefined;
var posEndEmail = undefined;
var email = undefined;
do {
if (tmp.toLowerCase().substring(0,4) !== 'test') { break; }
posStartEmail = tmp.toLowerCase().substring(4).indexOf('[');
posEndEmail = tmp.toLowerCase().substring(4).indexOf(']');
if (posStartEmail === -1 || posEndEmail === -1) { break; }
email = tmp.substring(posStartEmail+1+4,posEndEmail);
if (email.indexOf('@') === -1) { break; }
// all checks are done - do what you intend to do
alert ('All checks are ok')
break; // the most important break of them all
} while(true);
Solution 6 - Javascript
Javascript will throw an exception if you attempt to use a break;
statement inside an if else. It is used mainly for loops. You can "break" out of an if else statement with a condition, which does not make sense to include a "break" statement.
Solution 7 - Javascript
Actually there is no c3 in the sample code in the original question. So the if would be more properly
if (c1 && c2) {
//sequence 1
} else if (!c1 && !c2) {
// sequence 3
}
Solution 8 - Javascript
I had a similar problem today and found refactoring the conditional logic into a separate function to help.
I find it more readable than the labels and people are more comfortable with return
than break
. Inline functions are similar but the indentation can get a bit confusing.
In your case it would look like this.
function doThing() {
checkConditions();
// Rest of the code here
}
function checkConditions() {
if (c1) {
if (c2) {
return do1();
else {
return;
}
} else {
return do3();
}
}
Solution 9 - Javascript
Just remove the break. since it is already inside first if it will not execute else. It will exit anyway.
Solution 10 - Javascript
You need that it breaks the outer if statement. Why do you use second else?
IF condition THEN
IF condition THEN
sequence 1
// ELSE sequence 4
// break //?
// ENDIF
ELSE
sequence 3
ENDIF
sequence 4