JavaScript Operators
= is used to assign values.
+ is used to add values.
The assignment operator = is used to assign values to JavaScript variables.
The arithmetic operator + is used to add values together.
The value of x, after the execution of the statements above is 7.
JavaScript Arithmetic Operators
Arithmetic operators are used to perform arithmetic between variables and/or values.
Given that y=5, the table below explains the arithmetic operators:
Operator 
Description 
Example 
Result 
+ 
Addition 
x=y+2 
x=7 
 
Subtraction 
x=y2 
x=3 
* 
Multiplication 
x=y*2 
x=10 
/ 
Division 
x=y/2 
x=2.5 
% 
Modulus (division remainder) 
x=y%2 
x=1 
++ 
Increment 
x=++y 
x=6 
 
Decrement 
x=y 
x=4 
JavaScript Assignment Operators
Assignment operators are used to assign values to JavaScript variables.
Given that x=10 and y=5, the table below explains the assignment operators:
Operator 
Example 
Same As 
Result 
= 
x=y 

x=5 
+= 
x+=y 
x=x+y 
x=15 
= 
x=y 
x=xy 
x=5 
*= 
x*=y 
x=x*y 
x=50 
/= 
x/=y 
x=x/y 
x=2 
%= 
x%=y 
x=x%y 
x=0 
The + Operator Used on Strings
The + operator can also be used to add string variables or text values together.
To add two or more string variables together, use the + operator.
txt1="What a very";
txt2="nice day";
txt3=txt1+txt2; 
After the execution of the statements above, the variable txt3 contains "What a verynice day".
To add a space between the two strings, insert a space into one of the strings:
txt1="What a very ";
txt2="nice day";
txt3=txt1+txt2; 
or insert a space into the expression:
txt1="What a very";
txt2="nice day";
txt3=txt1+" "+txt2; 
After the execution of the statements above, the variable txt3 contains:
"What a very nice day"
Adding Strings and Numbers
The rule is: If you add a number and a string, the result will be a string!
Example
x=5+5;
document.write(x);
x="5"+"5";
document.write(x);
x=5+"5";
document.write(x);
x="5"+5;
document.write(x); 
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