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JavaScript

Posted by Dmitry Gavrikov
Dmitry Gavrikov
3,956 Points

print out variables

Hello,

I can't understand one thing. For instance, we have the current code. When we create a new var "message" it consists "<p>Hello, My name is " + person.name + "</p>"; but after creating a new variable it has already got different value, however, when we call the function "print" it prints out not last value but every line of var message? "Hello. My name is..." "I live in.." Thanks.

function print(message) {
  var div = document.getElementById('output');
  div.innerHTML = message;
}
var message = "<p>Hello, My name is " + person.name + "</p>";
message += "<p>I live in the " + person.country + "</p>";
print(message);

2 Answers

Jacob Mishkin
Jacob Mishkin
23,118 Points
Jacob Mishkin
Jacob Mishkin
23,118 Points

It's because you are concatenating the variable message by using the += operator.

the operator + contacts data together, in this case the variable message.

Mauro Teixeira
Mauro Teixeira
3,727 Points
Mauro Teixeira
Mauro Teixeira
3,727 Points

A small example to ilustrate what Jacob Mishkin said:

var value = 2;
value = 3; // the value is now 3
value += 4; // the value is now 3 (previous value) + 4 = 7;

basically, doing 

value + = 4;

is the same as doing 

value = value + 4;

It's the same with Strings, if you use the += operator, you won't "replace" the message with the one you want - you will in fact "add it" / contactenate it with the one already in the element.