var foo = '' + 2 + 2; //foo === '22'
var bar = 2 + 2 + '2'; //bar === '42'
var baz = 2 + '2' + 2; //baz === '222'
var qux = '2' + 2 + 2; //qux === '222'
console.log("The sum is " + baz + qux); //The sum is 222222
Basically, when you mix numbers with strings bad things start to happen. In order to avoid problems with addition and concatenation try to ensure that all of your operands are of the same type: numbers or strings. This will ensure that the plus operator is working in the expected mode and will not switch in the middle of you operation.
Thank you for reading, everyone.