I was wondering how JavaScript interpret the string numbers (i.e. "2"). for instance:
var car = { color: "red", model: "370"};
var anotherAge = ++(car.model) + 2;
or
var b=+"1" + 2; // returns 3
How JavaScript really works when it use ++("370")? I am looking for the way JavaScript behaves. What happens beyond?
It basically works like this:
var anotherAge = ++(car.model) + 2;
// ^^^^^^^^^^^^^
// coerce to numeric -> int(371)
var b=+"1" + 2;
// ^
// coerce to numeric -> int(1)
Once converted to a numeric expression, the remaining + operation will be interpreted as a mathematical operation rather than string concatenation.
Related
When i am writing 11.00 it is displaying 11.00.00 otherwise its working fine on rest
if(pos == -1)
{
document.getElementById("printCheckAmount").textContent = "$" + checkObj.checkAmount + ".00";
}
else
{
var integer = enterCheckAmount.substring(0,pos);
var decimals = enterCheckAmount.substring(pos+1);
while(decimals.length<2) decimals=decimals+'0';
enterCheckAmount = integer + '.' + decimals;
document.getElementById("printCheckAmount").textContent = "$" + checkObj.checkAmount;
}
JavaScript doesn't have a variable type for decimal numbers. It has only Number. If you want to display an integer as a decimal number with two zeros after the decimal point you can use the method toFixed.
Here is an example:
var myNumber = 11;
var myDecimalNumber = myNumber.toFixed(2);
console.log(myDecimalNumber) // will output 11.00
Thus there is no need to concatenate strings and add ".00" manually to your number.
Beyond this you can use the methods parseInt and parseFloat. Let's say you have a variable of type string with the value "11 pieces". You can get the integer with this line of code:
var myString = "11 pieces";
var myInteger = parseInt(myString, 10);
console.log(myInteger); // will output 11
If you have something similar like this, you are better off with this methods instead of cuting substrings.
I wish you a lot of success in refactoring your code and a warm welcome to the StackOverflow community.
I have to convert a working C# function to JavaScript so it executes client-side. Here's the C#...
// convert the cmac into a hex number so we can increment it and get the emac
long emacLong = Convert.ToInt64(_cmac, 16) + 1;
emac = emacLong.ToString("x12").ToUpper();
Here's what I have so far in JavaScript..
var emac = parseInt(cmac, 16) + 1;
emac = emac.toString(16);
The input is "0015D1833339". The output should be "0015D183333A". However, the JavaScript returns "15d183333a". I need to retain the leading 0's. Looks like the C# function accomplishes this with the "x12" parameter of .ToString. How do I accomplish this in JavaScript? I need to convert it to an integer, increment it by 1 and then convert back to a string with a length of 12 characters.
Easy way to pad hex number output when you know the exact length you desire is with something like this:
var emac = parseInt(cmac, 16) + 1;
emac = ("000000000000" + emac.toString(16)).substr(-12);
// or if you MUST have all caps....
emac = ("000000000000" + emac.toString(16)).substr(-12).toUpperCase();
This example is for length 12, if you need a different length, you would adjust the length of the 0 string and the substr param.
I have the following function that encrypts a string and I was hoping for a function that reverses the process.
function encryptStr(thisString)
{
retString = "";
/* Make retString a string of the 8-bit representations of
the ASCII values of its thisCharacters in order.
EXAMPLE: "abc" --> "011000010110001001100011"
since the ASCII values for 'a', 'b' and 'c'
are 97=01100001, 98=01100010 and 99=01100011
respectively
*/
for (i = 0, j = thisString.length; i < j; i++)
{
bits = thisString.charCodeAt(i).toString(2);
retString += new Array(8-bits.length+1).join('0') + bits;
}
/* Compress retString by taking each substring of 3, 4, ..., 9
consecutive 1's or 0's and it by the number of such consecutive
thisCharacters followed by the thisCharacter.
EXAMPLES:
"10101000010111" --> "10101401031"
"001100011111111111111" --> "0011319151"
*/
retString = retString.replace(/([01])\1{2,8}/g, function($0, $1) { return ($0.length + $1);});
return retString;
}
I tried to make a function and I'm probably doing it wrong because it's 50 lines already. I'm realizing that there's tons of error checking that needs to go on. For instance, I just realized a potential problem because JavaScript characters don't span the entire 127 ASCII values. Should I just give up? Is this a futile problem?
First, find the numbers in the string which are not 0 or 1. Then, expand them in the opposite way that the original function collapsed them. You can again use String.prototype.replace() here with a replacement function...
str.replace(/([2-9])([01])/g,
function(all, replacementCount, bit) {
return Array(+replacementCount + 1).join(bit);
});
Then, simply decode the bit stream back into characters with String.fromCharCode(). You'd need to chunk the stream into 8 bit chunks, and then perform the conversion. I chose to use Array.prototype.reduce() as it's quite suited to this task. Alternatively, you could use String.fromCharCode.apply(String, chunks.map(function(byte) { return parseInt(byte, 2); })) to get the resulting string.
Something like...
str.split(/(.{8})/g).reduce(function(str, byte) {
return str + String.fromCharCode(parseInt(byte, 2));
}, "");
Put it together, and you get a function like...
function decryptStr(thisString) {
return thisString.replace(/([2-9])([01])/g,
function (all, replacementCount, bit) {
return Array(+replacementCount + 1).join(bit);
}).split(/(.{8})/g).reduce(function (str, byte) {
return str + String.fromCharCode(parseInt(byte, 2));
}, "");
}
jsFiddle.
Also, remember to place var in front of your variable declarations, otherwise those variable identifiers will leak to the containing scope until they're resolved (which is usually the global object).
I am using the following script. But I am receiving a wrong result for x_b_bbetrag.
When do an calculation exp 100/108 I get 9.92 instead of 92.59.
What am I missing here?
Code below:
var betrag = 100
var kurs = 1
var minkl= 1
var msatz= 0.08
$("#x_b_betrag").change(function() {
var betrag = $("#x_b_betrag").val();
var kurs = $("#x_b_kurs").val();
var minkl =$("input[name='x_b_mwstinkl']:checked").val();
var msatz =$("input[name='x_b_mwst']:checked").val();
if (minkl == "1"){
$("#x_b_rechenbetrag").val((betrag * kurs).toFixed(2));
$("#x_b_bbetrag").val( ( (betrag * kurs) /(1 + msatz) ).toFixed(2));
}
Use parseFloat
multiplication, division and subtraction automatically parse string to number. for summation you need to parse it.
$("#x_b_bbetrag").val( ( (betrag * kurs) /(1 + parseFloat(msatz) ) ).toFixed(2));
///1 + "1" = 11 not 2
Parse your inputs into numbers.
For example :
var betrag = parseFloat($("#x_b_betrag").val());
MDN on parseFloat
The value of the msatz variable is not 0.08 but "0.08". It's a string, so when you add one to it, the number will be converted to a string so that they can be concatenated, and the result is "10.08" not 1.08. The string will implicitly be converted to a number when you use it in the division, as it's not possible to divide by a string.
Parse the string into a number:
var msatz = parseFloat($("input[name='x_b_mwst']:checked").val());
I am attempting to perform mathematical operations with JavaScript on values obtained from an attribute. The attribute is created via a PHP loop. I will give an example of one of the html tags containing the attributes, but keep in mind that there are many of these tags which contain unique attribute values.
The HTML:
The JavaScript(jQuery):
$("a[href^='secondary_imgs.php']").click(function(){
var pageWidth = $(window).width();
var maxshadowWidth = (Math.floor(pageWidth * 0.91808874)) - 2;
var mWidth = $(this).attr("mwidth");
var maxSecondaryWidth = mWidth + 60;
alert (maxSecondaryWidth);
if(maxSecondaryWidth <= maxshadowWidth) {
var shadowWidth = maxSecondaryWidth;
} else {
var shadowWidth = maxshadowWidth;
}
var shadowboxrel = 'shadowbox;width=' + shadowWidth;
$(this).attr('rel', shadowboxrel);
The operation doesn't seem to be working, and I have a feeling it has to do with my lack of experience using mathematical operations in javascript. In this case, I think something is wrong with my method of using the attribute value, in the mathematical operation.
For example, the above width attribute is defined as 593. I define the maxSecondaryWidth as mWidth + 60. I fired an alert to see what value I was getting. It should have been shown as 653, yet the value that is 'alerted' is 59360. Obviously I don't understand how to add, as the + is concatenating the two values, as opposed to adding them together. Could it have to do with needing to transform the attribute value from a string into an integer?
You have to convert to a number using parseInt(), otherwise + will do string concatenation:
var mWidth = parseInt($(this).attr("mwidth"), 10);
If the attribute can also be a float, use parseFloat() instead of parseInt().
Do this to make sure mwidth is a number:
var mWidth = parseInt($(this).attr("mwidth"), 10);
Otherwise, + will perform a string concatenation. Alternatively, if you need mwidth to be a floating point number, do this:
var mWidth = parseFloat($(this).attr("mwidth"));
You can do a couple things:
parseInt(mWidth, 10); // int
parseFloat(mWidth); // float
Number(mWidth); // number
otherwise javascript will believe it's a string.
Some less common conversions:
mWidth | 0; // int (javascript bitwise operations are 32-bit signed intergers)
+mWidth; // force Number
i think that you must do something safer (as it is always better);
You should check if it is a number or not:
DOM:
JS:
$("a[mwidth]").each(function(){
var $attr = $(this).attr('mwidth');
if(!isNaN($attr)){
sum += (parseInt($attr));
}
});
If you remove the condition the results will be NaN
Take a look at : http://jsfiddle.net/zVwYB/