Concatenating a String and Another Data Type

By Stephen Bucaro

To concatinate two or more strings, use + (the concatination operator). To concatinate a string and a number, also use the concatination operator. This is because JavaScript coerces (converts) the number to a string. Shown below is an example:

var amt = 4.35;
var total = "The total is " + amt;
alert(total);

Result: The total is 43.45

Using the + operator with two numbers will add the two numbers and return the sum. Shown below is an example:

var amt1 = 4.35;
var amt2 = 5.65;
var total =  amt1 + amt2;
alert(total);

Result: 10

But using the + operator with a number in a string data type and a number returns a string with an incorrect result. Shown below is an example:

var amt1 = 4.35;
var amt2 = "5.65";
var total =  amt1 + amt2;
alert(total);

Result: 4.355.65

To use the + operator with a number, or numbers, in a string data type requires passing the strings to either parseInt() or parseFloat() to convert the strings to numbers. An example is shown below.

var strNum1 = "43";
var strNum2 = "35";
var total = parseInt(strNum1) + parseInt(strNum2);
alert(total);

Result: 78

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