I am practicing the comparison operators in an if/else statement. My question is that I am expecting the window will give me a True alert, but instead it gave me the False alert. I thought the system will coerce num1 into 97 before it performs the comparison.
Here is my code:
var num1 = "a";
var num2 = 99999;
if (num1 <= num2) {
window.alert("True");
}else {
window.alert("False");
}
I believe the answer to your question has to do with implicit conversions which are happening here. Consider the following line of code:
console.log(99999 + "a")
This will output 99999a, and it won't convert the "a" string to a number. Assuming the same happens with your code snippet, it explains the observations. What we are seeing is consistent with this:
var num1 = "a";
var num2 = "99999";
if (num1 <= num2) {
console.log("True");
} else {
console.log("False");
}The reason why this is false is that the letter a is lexicographically greater than any single digit character. And since JavaScript is comparing two strings, they are sorting as text, and the first character is all which needs to be examined to render an ordering.
You can use .codePointAt() to get the code point of the charcter
var num1 = "a";
var num2 = 99999;
if (num1.codePointAt(0) <= num2) {
window.alert("True");
} else {
window.alert("False");
}
the above condition is translated as
if(parseInt(num1)<= parseInt(num2)) {
//something
}parseInt(num1) returns NaN (Not a number) and NaN is, by definition, not less than, equal to, or greater than any other number. Hence the output is false.
num1="a" is a string and in the comparison num1<=num2, num2 is a number. Implicit conversion happens here and num2 is converted into a string. There are several ways to convert a string(of type "345", etc) into a number:
Number()
parseInt()
parseFloat()
bitwise ~~
But the string num1 contains a character so these functions return NaN(Not a number).Hence we cannot convert the string of characters into a number.
Your purpose can be achieved using the charCodeAt() function as follows :
var num1="a";
var num2=9999;
if(num1.charCodeAt(0)<=num2){
window.alert("True");
}else{
window.alert("False");
}
aas number97?