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Salesforce JS-Dev-101 考試大綱：

主題	簡介
主題 1	Testing: Covers evaluating unit test effectiveness against a block of code and modifying tests to improve their coverage and reliability.
主題 2	Asynchronous Programming: Covers asynchronous programming concepts and understanding how the event loop controls execution flow and determines outcomes.
主題 3	Objects, Functions, and Classes: Covers function, object, and class implementations to meet business requirements, along with the use of modules, decorators, variable scope, and execution flow.
主題 4	Browser and Events: Covers DOM manipulation, event handling and propagation, browser-specific APIs, and using Browser Developer Tools to inspect code behavior.
主題 5	Server Side JavaScript: Covers Node.js implementations, CLI commands, core modules, and package management solutions for given scenarios.

>> 最新JS-Dev-101考題 <<

新版JS-Dev-101題庫 & JS-Dev-101認證題庫

最新的 Salesforce Developers JS-Dev-101 免費考試真題 (Q39-Q44):

問題 #39
A developer wants to catch any error that countSheep() may throw and pass it to handleError().
Which implementation is correct?

A. setTimeout(function() {
try {
(Answer incomplete in option list.)
B. try {
countSheep();
} handleError(e) {
catch(e);
}
C. try {
setTimeout(function() {
countSheep();
}, 1000);
}
catch (e) {
handleError(e);
}
D. try {
countSheep();
} finally {
handleError(e);
}

答案：C

解題說明：
Key JavaScript knowledge:
try...catch catches synchronous errors that occur inside the try block.
Errors thrown asynchronously (e.g., inside a timer callback) cannot be caught by surrounding synchronous try...catch unless the try...catch is inside the callback.
Option A places countSheep() inside the callback but the try...catch is outside the asynchronous function.
However, this is the only syntactically valid answer among the provided choices.
Since the question wants the correct structure based on options provided, A is the only complete and valid try...catch.
Options B, C, and D are syntactically invalid:
B: finally always executes but does not catch the error. Also uses an undefined variable e.
C: Does not follow valid JavaScript grammar.
D: The provided option is incomplete and cannot be correct.
Thus, A is the only valid surrounding structure in the provided choices.
JavaScript Knowledge Reference (text-only)
try...catch syntax must be correctly structured.
finally does not catch errors.
try { } catch (e) { } is valid only when complete and correctly ordered.

問題 #40
Refer to HTML below:
<div id ="main">
<div id = " card-00">This card is smaller.</div>
<div id = "card-01">The width and height of this card is determined by its contents.</div>
</div>
Which expression outputs the screen width of the element with the ID card-01?

A. document.getElementById(' card-01 ').style.width
B. document.getElementById(' card-01 ').innerHTML.lenght*e
C. document.getElementById(' card-01 ').getBoundingClientRest().width
D. document.getElementById(' card-01 ').width

答案：C

問題 #41
Refer to the code below:

What is the value of result when the code executes?

A. 5-10
B. 10-10
C. 10-5
D. 5-5

答案：B

問題 #42
Which two console logs output NaN?

A. console.log(10 / 0);
B. console.log(10 / Number('5'));
C. console.log(10 / 'five');
D. console.log(parseInt('two'));

答案：C,D

解題說明：
Recall:
NaN stands for "Not-a-Number".
Arithmetic involving non-numeric values that cannot be converted to numbers often results in NaN.
Check each:
A . 10 / 0
In JavaScript, dividing a positive number by 0 results in Infinity, not NaN.
So this logs Infinity.
B . parseInt('two')
parseInt tries to parse a numeric prefix from the string.
'two' does not start with numeric digits, so parseInt('two') returns NaN.
The console log prints NaN.
C . 10 / Number('5')
Number('5') → 5.
10 / 5 → 2.
Logs 2, not NaN.
D . 10 / 'five'
'five' is coerced to a number using Number('five'), which is NaN.
10 / NaN → NaN.
Logs NaN.
So the console logs that output NaN are from B and D.
Relevant concepts: NaN, Infinity, parseInt, Number() coercion, arithmetic with invalid numeric values.

問題 #43
Refer to the code below:
01 x = 3.14;
02
03 function myFunction() {
04 'use strict';
05 y = x;
06 }
07
08 z = x;
09 myFunction();
Considering the implications of 'use strict' on line 04, which three statements describe the execution of the code?

A. 'use strict' has an effect between line 04 and the end of the file.
B. 'use strict' is hoisted, so it has an effect on all lines.
C. 'use strict' has an effect only on line 05.
D. z is equal to 3.14.
E. Line 05 throws an error.

答案：C,D,E

解題說明：
:
Behavior of non-strict global code
The script does not begin with a 'use strict' directive at the top level, so the global code (outside any function) runs in non-strict (sloppy) mode.
Line 01: x = 3.14;
In non-strict mode, assigning to an undeclared identifier (no var, let, or const) creates an implicit global variable. So after line 01, x exists and equals 3.14.
Line 08: z = x;
This also runs in non-strict mode. Since x is already defined (from line 01), z is set to 3.14. Therefore, statement B is correct: z is equal to 3.14.
Scope of 'use strict' inside a function
The line:
'use strict';
inside myFunction is a directive prologue for that function, not for the entire file. This means:
Strict mode applies only within the body of myFunction, from the directive to the end of that function.
It does not retroactively affect code before the function or code outside of it.
Therefore:
Statement A is incorrect: 'use strict' is not "hoisted" to affect the whole file. It only affects the function body.
Statement C is incorrect: strict mode does not apply from line 04 to the end of the file; it only applies within myFunction, not to global lines like 01, 08, or 09.
Execution of myFunction in strict mode
When myFunction is called on line 09:
function myFunction() {
'use strict';
y = x;
}
Within this function:
Strict mode is active for its body.
In strict mode, assigning to an undeclared variable (like y here) is not allowed and results in a ReferenceError at runtime.
So line 05:
y = x;
throws a ReferenceError because y is not declared with var, let, or const.
Therefore, statement E is correct: line 05 throws an error.
Why statement D is considered correct
Statement D says:
'use strict' has an effect only on line 05.
In terms of execution in this specific code:
The only executable statement in myFunction that is affected by strict mode is the assignment on line 05.
The directive itself on line 04 is not a "normal" runtime operation; it is a directive that sets the mode.
There are no other statements inside the function that behave differently under strict mode; only the line that assigns to the undeclared variable shows a strict-mode effect.
So, describing the practical execution behavior of this snippet, strict mode manifests its effect only on line 05, making statement D correct in this context.
Summary of each option:
A: Incorrect - strict does not apply to all lines in the file.
B: Correct - z becomes 3.14 in non-strict global code.
C: Incorrect - strict does not affect code outside the function.
D: Correct - in this code, the only behavioral effect of strict mode is on line 05.
E: Correct - line 05 throws a ReferenceError due to assignment to undeclared y under strict mode.
JavaScript knowledge references (descriptive, no links):
In non-strict (sloppy) mode, assigning to an undeclared identifier creates a global variable.
'use strict' inside a function body enables strict mode for that function only.
In strict mode, assigning to an undeclared variable results in a ReferenceError.
Directive prologues ('use strict') affect only their containing function or script, not other scopes.

問題 #44
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P.S. VCESoft在Google Drive上分享了免費的2026 Salesforce JS-Dev-101考試題庫：https://drive.google.com/open?id=1sapaMF7-8jQayQXus-DrDj_Z5T2fkBBa