将多个if-else语句转换为对象的大小写转换

Question

I have an object in which I have to verify different values using multiple if-else statements, like below is sample javascript snippet:

if(properties.values.a > 0 ){

}else if(properties.values.b > 0){

}else if(properties.values.c > 0){

}else if(properties.values.d > 0){

}else if(properties.values.e > 0){

}else{

}

I am willing to replace this multiple if-else statement into switch-case. Now I wonder if that is possible for objects or not? If possible, how should be going towards it?

Answer 1

Switch is not supposed to work like this. So, no, this is not supported. As a workaround you could do this

switch (true) {
    case (properties.values.a > 0):
        ...
    case (properties.values.b > 0):
        ...
    case (properties.values.c > 0):
        ...
    case (properties.values.d > 0):
        ...
    case (properties.values.e > 0):
        ...
}

Still, is pretty ugly so i suggest you stick to if/else.

Answer 2

You can do that with a for in loop:

 o = { a:0, b:0, c:1, d:0 }; for(var p in o) { if (o[p] > 0) { //... console.log(o[p]); break; } } 

Answer 3

You could use an array with the wanted keys and use iterate with a short circuit if a value is found.

If no one is found call callOther .

['a', 'b', 'c', 'd', 'e'].some(k => {
    if (properties.values[k] > 0) {
        callThis();
        return true;
    }
}) || callOther();

Answer 4

In JavaScript you can only use switch to check for equality. You can't check whether a > b using a switch.

If you want a more elegant solution, that I particularly would only use if I needed to check a huge amount of rules, is to do something like this:

const checkers = [];
checkers.push([p => p.values.a > 0, () => { /* do something */ }])
checkers.push([p => p.values.b > 0, () => { /* do something */ }])
...
checkers.filter(checker => checker[0](property)).forEach(checker => checker[1]())

In the above example, checkers is an array of arrays in which the first element is a predicate function and the second is a function that should execute if the predicate is true.

But again... For most cases you just do an if/else as you described.

Also, if you want to check if a value is greater than 0, you might use just if(a) , because if a is not 0 , then it's truthy, otherwise it's falsy.

EDIT

Apparently, technically, you can use logical expressions within switch statements, even though it seems hacky =/