vararr=[1,12,4,124.45,8,99998,456];
Math.max.apply(Math,arr);
Math.min.apply(Math,arr);
                            

Array.prototype.max=function(){
varmax=null;
for(variinthis){
varv=parseFloat(this[i]);
if(max==null){
max=v;
}else{
max=v>max?v:max;
}
}
returnmax;
}
test:
vara=[1,3,9,5,7];
a.max()
output:9