JavaScriopt中的范围

// Set a global variable, foo,equa to test
var foo = "test";

//Within an if block
if(true){
    // set foo equal to 'new test'
    // NOTE:This is still within the global scope!
    var foo = "new test";
}

//As we can see here, as foo is now equal to 'new test'
alert(foo == "new test");

//Create a function that will modify the variable foo
function test(){
    var foo = "old test";
}

//However, when called, 'foo' remains within the scope of the function
test();

//Which is confirmed, as foo is still equal to 'new test'
alert(foo == "new test");

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var test = "test";

alert(window.test == test );

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// A function in which the value of foo is set
function test(){
    foo = "test"
}

//Call the function to set the value of foo
test();

//We see that foo is now globally scoped
alert(window.foo == "test" );