How to transform if-else statement to equivalent switch statement? I’m gonna show an example. Take a look at the following if-else statement :
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function number(num){ if(num < 0){ alert("Number is negative"); } else if(num >= 0 && num <= 100){ alert("Number is betwwen 0 and 100 (inclusive)"); } else if(num > 100){ alert("Number is greater than 100"); } else{ alert("This is not a number"); } } |
First wrap the if-else inside switch block :
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function number(num){ switch(condition){//I'll tell the condition later if(num < 0){ alert("Number is negative"); } else if(num >= 0 && num <= 100){ alert("Number is betwwen 0 and 100 (inclusive)"); } else if(num > 100){ alert("Number is greater than 100"); } else{ alert("This is not a number"); } } } |
if and all if-else blocks become our case blocks, and else will become default case :
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function number(num switch(condition){//I'll condition later case (num < 0) : { alert("Number is negative"); } case (num >= 0 && num < 100) : { alert("Number is betwwen 0 and 100 (inclusive)"); } case (num > 100) : { alert("Number is greater than 100"); } default : { alert("This is not a number"); } } } |
And don’t forget to add break :
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function number(num switch(condition){//I'll condition later case (num < 0) : { alert("Number is negative"); } break; case (num >= 0 && num < 100) : { alert("Number is betwwen 0 and 100 (inclusive)"); } break; case (num > 100) : { alert("Number is greater than 100"); } break; default : { alert("This is not a number"); } } } |
All cases are actually boolean (num < 0, num >= 0 && num < 100 and num > 100 are actually returning boolean). One of the case will eventually become true depending on the value of num. So our switch condition should be a boolean (true) so that it will match one of the cases :
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function number(num switch(true){ case (num < 0) : { alert("Number is negative"); } break; case (num >= 0 && num < 100) : { alert("Number is betwwen 0 and 100 (inclusive)"); } break; case (num > 100) : { alert("Number is greater than 100"); } break; default : { alert("This is not a number"); } } } |
Done.
