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Expressions

Expressions:

  • 1 + 2
  • a + b (assuming existing variables a and b)
  • year + 10 (assuming existing variable year)
  • age === 18 (assuming existing variable age)
  • age >= 18 (assuming existing variable age)

Computed values:

  • 1 + 2 produces 3
  • a + b produces the sum of a and b (assuming a and b are numbers)
  • year + 10 produces a number which is the result of adding 10 to the variable year
  • age === 18 produces a boolean (either true or false, depending on the age)
  • age >= 18 also produces a boolean depending on the age

Javascript does some intermediary steps:

let year = 2000
console.log(year + 8)

There is a calculation of year + 8 implied in there

Summary

  • An expression is a combination of one or more variables, functions, and operators that the programming language computes to produce a value.
  • 5 + 4 is an example of an expression that produces a value of 9.
  • counter >= 10 is an example of an expression that produces a boolean (either true or false), depending on the value of the variable counter.
  • When there are expressions, JavaScript goes through some intermediary steps to compute the value from the expression.
  • console.log(expression) is often mentioned in documentation, meaning that console.log expects to receive an expression.
  • An expression produces a value and can be written wherever a value is expected.