如何保存返回值？

Question

Does a method/function's call statement hold its return value similar to a how a variable name holds a value?

For example:

function Jump(height) {
    return height * 2;
}
Jump(3);       //Is the call statement 'Jump(3)' equal the return value of 6 similar to

var x = 3;  //how the variable 'x' is equal to the value of 3?

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Edit: I gave the wrong impression by naming the variable and function the same name. I was purely using the variable as a comparison in understanding how return values are saved. I'll word/structure my question better next time.

Answer 1

functions and variables share the same namespace. You defined the function Jump and then called it (but didn't actually assign the results of the function (what was returned)), so it returned 6 but then you didn't actually store it anywhere. Then you overwrote your function by redefining it as a variable with the same name, and just assigned it the value of 3

Answer 2

A little about expressions

Following your edit, it seems you're asking about expressions .

An expression is basically a snippet that has a value . In your example both Jump(3) and var x = 3 are expressions, as both have a value. In other words, Jump(3) is an expression with the value 6 and (x=3) is actually an expression which evaluates to 3 .

The only difference between the two is that the first expression also assigns a value with the assignment operator (ie = ), while the second expression is "just" a value. For that matter, in your example, the variable x is also an expression that evaluates to 3 .

For more on this subject see MDN - Expressions and operators in Javascript

More to the point

This means that when you pass an argument to a function by-value , you're essentially passing the value of the expression. So in your example, Jump(x) , Jump(3) , Jump((x=3)) and Jump(Jump(1.5)) would all evaluate to 6 .

Naturally, it's much less costly to store the value of common operations in a variable that would be quickly evaluated as an expression, than to have the calculation done each time the expression is evaluated.