var arr = [1,2,5,4,5,6,7,8,5];
for(var i = 0;i<arr.length;i++){
    if(arr[i]===5){
        arr.splice(i,1);
        i--;
    }
}
console.log(arr); //[1,2,4,6,7,8]

var arr = [2, 3, 5, 7];
arr = arr.filter(item => item !== 5);

var arr = [2, 3, 5, 7];
for (let i = arr.length - 1; i >= 0; i--) {
    if (arr[i] === 5) {
        arr.splice(i, 1);
    }
}