How can I use javascript to add a number (any number between 0-100) followed by a underscore, before the variable value?
Example:
2000 becomes 12_2000 //a number of my choice is added followed by an underscore
hello becomes 12_hello
The number (12 in this case) is a constant chosen by me!
Thanks
i + '_' + x where i is the number and x is an arbitrary value.
Just use string concatenation:
var res = '12_' + myNum;
Or with a variable prefix:
var res = prefix + '_' + myNum;
This is just basic string concatenation, which can be done with the + operator:
var num = 2000;
"12_" + num;
// "12_2000"
var_name = "2000";
output = "12_" + var_name;
function prefixWithNumber(value, number) {
return number + "_" + value;
}
This expression is evaluated as (number + "_") + value. Since one of the operants in the first addition is a string literal, the second argument number is converted (coerced) to a string. The result is a string, which causes the third argument to be converted to a string as well.
This is what the JS engine does behind the scenes:
(number.toString() + "_") + value.toString();
Maybe you're looking for something like this:
Object.prototype.addPrefix = function(pre){
return pre + '_' + this;
};
This allows code like:
var a = 5;
alert(a.addPrefix(7));
or even:
"a string".addPrefix(7);
Joining an array can be faster in some cases and more interesting to program than "+"
[i, '_', myNum].join('')
