Function from js-file becomes global for all files.

function say() {
    console.log("BAR")
}

function say() {
    console.log("FOO")
}
this.say = say;

...
import "Foo.js" as Foo
import "Bar.js" as Bar

...

Component.onCompleted: {
    Foo.say();
    Bar.say(); // !
    say();     // !!!
}

qml: FOO
qml: FOO
qml: FOO