I am trying to implement a simple javascript-html calculator. What i want to do is,typing only one '.' by the user. How can i control this ? Here is the code that i tried.

I can already find the number of '.' but i'am confused now also this replaceAll function is not replacing '.' with empty string.

String.prototype.replaceAll = function(search, replace)
{
    //if replace is null, return original string otherwise it will
    //replace search string with 'undefined'.
    if(!replace) 
        return this;

    return this.replace(new RegExp('[' + search + ']', 'g'), replace);
};
function calculate(){
    var value = document.calculator.text.value;
    var valueArray = value.split("");
    var arrayLenght = valueArray.length;
    var character = ".";
    var charCount = 0;
    for(i=0;i<arrayLenght;i++){
        if (valueArray[i]===character) {
            charCount += 1; 
        }
    }
    if(charCount>1){
        var newValue=value.replaceAll(".","");
        alert(newValue);    
    }
}