Big talk design pattern described in Javascript language (1)

I have read the online trial part of this book. I used JavaScript to rewrite the C # source code in this book.

Chapter 1 source code rewriting in section 1.1:

Code
Program = {
Main: function (){
If (! Document. getelementbyid) return;
VaR A = Document. getelementbyid ('numa'). value;
VaR B = Document. getelementbyid ('operator'). value;
VaR c = Document. getelementbyid ('numb'). value;
VaR d = '';
If (B = '+ '){
D = Number (A) + number (C );
}
If (B = '-'){
D = Number (a)-number (C );
}
If (B = '*'){
D = Number (a) * Number (C );
}
If (B = '/'){
D = Number (a)/number (C );
}
Document. getelementbyid ('compute'). onclick = function (){
Return document. getelementbyid ('result'). innerhtml = D;
}
}
}

HTML code:

Code
<P>
<Label for = "NUMA"> enter the number A: </label>
<Input type = "text" id = "NUMA" value = ""/>
</P>
<P>
<Label for = "operator"> select the operator number (+,-, *,/): </label>
<Input type = "text" id = "operator" value = ""/>
</P>
<P>
<Label for = "Numb"> enter the number B: </label>
<Input type = "text" id = "Numb" value = ""/>
</P>
<P>
<Button id = "compute"> computing </button>
</P>
<P>
<Span id = "result"> </span>
</P>

 

Chapter 1 source code rewriting in section 1.3:

Code
Program = {
Main: function (){
If (! Document. getelementbyid) return;
Try {
VaR snuma = Document. getelementbyid ('numa'). value;
VaR soperate = Document. getelementbyid ('operate'). value;
VaR snumb = Document. getelementbyid ('numb'). value;
VaR sresult = '';
Switch (soperate ){
Case '+ ':
Sresult = (number (snuma) + number (snumb). tostring ();
Break;
Case '-':
Sresult = (number (snuma)-number (snumb). tostring ();
Break;
Case '*':
Sresult = (number (snuma) * Number (snumb). tostring ();
Break;
Case '/':
If (snumb! = '0 ')
Sresult = (number (snuma)/number (snumb). tostring ();
Else
Sresult = 'divisor cannot be 0 ';
Break;
}
}
Catch (Ex ){
Console. Log ('your input is incorrect: '+ ex );
}
Document. getelementbyid ('compute'). onclick = function (){
Return document. getelementbyid ('result'). innerhtml = sresult;
}
}
}