后续的javascript函数中未定义全局变量

Question

I had some code that essentially was like this:

TestFunction();
const pi = 3.14;

function TestFunction()
{
    alert("pi="+pi);
}

The code failed because 'pi' was undefined. I scratched my head for a long time but then realized that the code was not being parsed linearly. When the function was called, the function "TestFunction" was parsed, but the constant had not yet been parsed.

This occurred with Safari and Chrome. I don't know if all browsers would parse in the same way. It might work with some.

Answer 1

Moving the definition of the constant before the first call to the function solved the problem.

const pi = 3.14;

TestFunction();

function TestFunction()
{
    alert("pi="+pi);
}