Kyle Simpson is an Open Web Evangelist from Austin, TX, who's passionate about all things JavaScript. He's an author, workshop trainer, tech speaker, and OSS contributor/leader.
Quotes
bsvmbo1o qolhas quoted2 years ago
Expressions Statements are made up of one or more expressions. An expression is any reference to a variable or value, or a set of variable(s) and value(s) combined with operators.
For example:
a = b * 2;
This statement has four expressions in it:
• 2 is a literal value expression.
• b is a variable expression, which means to retrieve its current value.
• b * 2 is an arithmetic expression, which means to do the multiplication.
• a = b * 2 is an assignment expression, which means to assign the result of the b * 2 expression to the variable a (more on assignments later).
A general expression that stands alone is also called an expression statement, such as the following:
b * 2;
This flavor of expression statement is not very common or useful, as generally it wouldn’t have any effect on the running of the program —it would retrieve the value of b and multiply it by 2, but then wouldn’t do anything with that result.
A more common expression statement is a call expression statement (see ), as the entire statement is the function call expression itself: alert( a );
bsvmbo1o qolhas quoted2 years ago
perators are how we perform actions on variables and values.
We’ve already seen two JavaScript operators, the = and the *.
The * operator performs mathematic multiplication. Simple enough, right?
The = equals operator is used for assignment—we first calculate the value on the right-hand side (source value) of the = and then put it into the variable that we specify on the left-hand side (target variable).
This may seem like a strange reverse order to
specify assignment. Instead of a = 42, some
might prefer to flip the order so the source value
is on the left and the target variable is on the
right, like 42 -> a (this is not valid JavaScript!).