Salesforce JavaScript-Developer-I - Salesforce Certified JavaScript Developer (JS-Dev-101)

Comprehensive and Detailed Explanation:

" Salesforce " indices: S(0) a(1) l(2) e(3) s(4) f(5) …

A / C (substring(0, 5)):

substring(start, end) returns characters from start up to but not including end.

str.substring(0, 5) → characters at indices 0,1,2,3,4 → " Sales " .

D (substr(0, 5)):

substr(start, length) returns length characters starting at start.

str.substr(0, 5) → 5 chars from index 0 → " Sales " .

B is invalid because s is not defined; it should be 0. So the two correct statements are A and D.

The correct answers are A and B .

The original question contains a typing error where 66 should be corrected to the logical AND operator:

& &

A is correct because it first evaluates the logical AND expression and then converts the final result to a Boolean:

Boolean(exp1 & & exp2)

The & & operator returns the first falsy value or the last truthy value. Wrapping the result in Boolean() ensures the final result is strictly either:

true

or:

false

Example:

Boolean( " hello " & & 123);

This returns:

true

B is also correct because it converts both expressions to Boolean values first, then applies logical AND:

Boolean(exp1) & & Boolean(exp2)

This guarantees that both sides of the & & operation are Boolean values.

Example:

Boolean( " hello " ) & & Boolean(123);

This returns:

true

C is incorrect because it uses the bitwise AND operator:

&

This is not the same as logical AND:

& &

Bitwise AND converts values into numbers and compares their binary representation. It does not reliably return a Boolean logical result.

D is incorrect as written because the question gives the expressions as exp1 and exp2, but option D uses var1 and var2. After correction, it would be the same idea as option B.

Therefore, the verified answers are A and B .

objA is created with:

{ value: 10 }

objB = objA; Objects in JavaScript are assigned by reference , not copied. So objA and objB refer to the same object in memory.

The function:

changeValue(obj) {

obj.value = obj.value / 2;

}

When called as changeValue(objB), it updates the value property of the shared object :

value = 10 / 2 → 5

Therefore:

objA.value === 5

Because objA and objB refer to the same object, the change is reflected in both.

JavaScript Knowledge References (text-only)

Objects are stored and passed by reference.

Mutating an object inside a function mutates the original object.

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Current behavior:

Clicking < td > triggers the click event on row1, then bubbles up to < table > .

printMessage runs, logs " Row log " , then event.stopPropagation() stops the event from bubbling to the table.

So " Table log " never appears.

To allow the table’s inline onclick to run after the row handler:

Remove the propagation stop:

function printMessage(event) {

console.log( ' Row log ' );

// event.stopPropagation(); // remove this

}

Now the event bubbles:

printMessage logs " Row log " .

The table’s onclick runs, logging " Table log " .

Option A only changes capture/bubble phase but still stops propagation. C does nothing meaningful (stopPropagation takes no arguments). B removes the row handler entirely.