Largest Time for Given Digits LeetCode solution in JavaScript

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var largestTimeFromDigits = function(arr) {
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    let max=-1;
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    for(let A=0; A<4; A++){
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        for(let B=0; B<4; B++){
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			if(B==A){continue};
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            for(let C=0; C<4; C++){
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				if(C==A||C==B||arr[C]>=6){continue};
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                for(let D=0; D<4; D++){
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					if(D==A||D==B||D==C){continue};
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                    let time=arr[A]*1000+arr[B]*100+arr[C]*10+arr[D];
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                    if(time<2400){max=Math.max(max, time));
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                }
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            }
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        }
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    }
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	// Case1: max<0, which means NOTHING VALID -> return ""
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	// Case2: max isn't 4 digits. i.e.[0,0,0,0] -> padStart to make "0000"
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    let output=max.toString().padStart(4,0);
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    return max<0? "": output.substr(0,2)+":"+output.substr(2);
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};