How to check if all variables are different?
Is it possible to check if all the variables are different from each other?
var a = 1, b = 2, c = 3, d = 4;
if(a != b && a != c && a != d && b != a && b != c && b != d && c != a && c != b && c != d && d != a && d != b && d != c){
//All numbers are different
}
eg
if(a != b != c != d){
}
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You can store them all in an object and check if the number of keys matches the number of variables used, for example
var dummy = {};
dummy[a] = true;
dummy[b] = true;
dummy[c] = true;
dummy[d] = true;
console.log(Object.keys(dummy).length === 4);
If the values are different, then a new key will be created each time, and the number of keys will be equal to the number of variables used.
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As Denys Séguret commented, if you have the correct structure for your data, then it can be done in a more elegant way.
However, with what you have, you can still simplify as you can remove duplicate checks.
For example, you check that a! = B and then later that b! = A. These two checks are actually the same, only in a different order.
Removing all duplicates gives you ...
if(a != b && a != c && a != d && b != c && b != d && c != d)
It's a little easier, although you're still better off structuring your data.
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Another way to use arrays
var a =10, b = 20, c=30, d =40, e =50;
alert(isVariablesDifferent(a,b,c,d,e));
function isVariablesDifferent(){
var params = Array.prototype.slice.call(arguments);
for(var i = 0; i < params.length; i++){
if(params.lastIndexOf(params[i]) !== i){
return false;
}
}
return true;
}
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Make the array a variable. Iterate everything from first to last element and compare or otherwise hardcoded as shown below.
var a = 1, b = 2, c = 3, d = 4;
if(a != b && a != c && a != d && b != c && b != d && c != d)
alert('all the variables are unique');
Link to my example code in jsfiddle
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Another solution is push
variables in an array:
var a = 1,
b = 2,
c = 3,
d = 4;
var arr = [];
arr.push(a);
arr.push(b);
arr.push(c);
arr.push(d);
var sorted_arr = arr.sort(); // You can define the comparing function here.
// JS by default uses a crappy string compare.
var results = [];
for (var i = 0; i < arr.length - 1; i++) {
if (sorted_arr[i + 1] == sorted_arr[i]) {
results.push(sorted_arr[i]);
}
}
alert(results);
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I find it difficult to imagine a quality answer without context, but since ECMA-Script 5 there is a function Array.prototype.every
to check if all elements of an array match a boolean expression. That is, you can express the same problem as follows:
var a = 1, b = 2, c = 3, d = 4;
if(
[b, c, d].every(function(someVar) { return someVar != a; })
&& [a, c, d].every(function(someVar) { return someVar != b })
&& [a, b, d].every(function(someVar) { return someVar != c })
&& [a, b, c].every(function(someVar) { return someVar != d })
) {
alert("all different!");
}
Or check how you can simplify the implementation of the function different(...)
before Array.prototype
(or you can implement it as a property of some custom object or as a normal procedural function ...).
Array.prototype.different = function() {
var results = [];
for(var i = 0; i < this.length; i++) {
// This is to clone the array so we don't modify the source one
var arrayCopy = [].concat(this);
// This drops the variable value to check and returns it
var varValueToCheck = arrayCopy.splice(i, 1);
// Then we use every to check that every variable value doesn't
// equal current variable value to compare
results.push(arrayCopy.every(
function(varValue) {
return varValue != varValueToCheck;
})
);
}
// Once we've got all boolean results, we call every() on
// boolean results array to check that all items are TRUE
// (i.e. no variable equals to other ones!)
return results.every(function(result) { return result; });
};
// This should avoid that other libs could re-define "different"
// function, and also it should avoid for..in or forEach issues
// finding unexpected functions, as this function will be hidden
// when iterating Array.prototype
Object.defineProperty(Array.prototype, "different", {
enumerable: false,
configurable: false,
writable: false
});
var a = 1, b = 2, c = 3, d = 4;
// Simplified check!
if([a, b, c, d].different()) {
alert("also all different!!!");
}
Now the problem might be that simplifying a statement if
like yours with something like my suggestion is overkill or not, but that will depend on your actual use.
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I made a function to test this for you. This can be costly with large datasets.
Here is the fiddle: https://jsfiddle.net/Luqm8z7b/
function uniqueTest(ary){
for(var i=ary.pop(); ary.length > 0;i=ary.pop()){
for(var j = 0; j < ary.length; j++){
if(i === j) return false;
}
}
return true;
}
var a = 1, b = 2, c = 3, d = 4;
var list = [];
list.push(a, b, c, d);
console.log(uniqueTest(list));
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