The document discusses JavaScript and its relationship to HTML documents and the DOM. It explains that JavaScript can access and modify HTML elements using the DOM and defines global JavaScript objects and variables like window. Functions in JavaScript allow for code reuse and scoping of variables to local blocks of code.

1. JS
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3. • javascript
• javascript
• DOM HTML
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4. JS
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5. JS
•
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6. JS
•
• ≠
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7. JS
•
• ≠
• a=b b a
b a
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8. JS
•
• ≠
• a=b b a
b a
•
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9. • JS window
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10. window
window
Document
Number
String
Object
etc...
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11. window
window
Document window
Number
window var
String
Object
etc... var
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12. • var
• function
•
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13. •
•
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14. function test1(){
var a = 0;
function inner(){
return a++;
//test1 a inner
}
return inner //inner
}
var b = test1();
alert(b());//0
alert(b());//
var c = test1();
alert(c());//0
alert(b());//2
alert(c());//1
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15. •
• window
•
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