Array And Function MCQs with Explanations

If you omit a value from an array literal, the omitted element is given the value.

a1 has an element with index 0 and a2 has no element with index 0.

Arrays have a pop() method (it works with push()) that reduces the length of an array by 1 but also returns the value of the deleted element.

The reverse() followed by a join() will reverse the respective array and will store the reversed array in the memory.

The unshift() and shift() methods behave much like push() and pop(), except that they insert and remove elements from the beginning of an array rather than from the end. unshift() adds an element or elements to the beginning of the array, shifts the existing array elements up to higher indexes to make room, and returns the new length of the array. shift() removes and returns the first element of the array, shifting all subsequent elements down one place to occupy the newly vacant space at the start of the array.

The map() method passes each element of the array on which it is invoked to the functionyou specify, and returns an array containing the values returned by that function.

The typeof property is used to identify the array type.

The function definitions begin with the keyword function followed by an identifier that names the function and a pair of parantheses around a comma-separated list of zero or more identifiers.

The above code snippet returns undefined.

The function name is optional for functions defined as expressions. A function declaration statement actually declares a variable and assigns a function object to it.

The return statement causes the function to stop executing and to return the value of its expression (if any) to the caller.

If the return statement does not have an associated expression, it returns the undefined value.

Functions with no return value are sometimes called procedures.

The above code snippet contains nested function in which the function hypotenuse(a,b) has another function inside its scope, function square(x). The interesting thing about nested functions is their variable scoping rules. They can acceess the parameters and variables of the function (or functions) they are nested within.

The above code defines and invokes a function to determine if we’re in strict mode.

The code above is an invocation expression: it includes a function expression o.m and two argument expressions, x and y.

Even if the string value passed as a parameter to eval does represent a numeric value the use of eval() results in an error being generated.

Function name is optional for functions defined as expressions. Function expressions are sometimes defined and immediately invoked.

The parseInt() function returns the first integer contained in the string or 0 if the string does not begin with an integer.

A method is nothing more than a JavaScript function that is stored in a property of an object. If you have a function f and an object o, you can define a method named m of o with the following line: o.m = f;

You can always omit a pair of empty parentheses in a constructor invocation.

The state stored in d is 1 because d was not reset.

The code above creates 10 closures, and stores them in an array. The closures are all defined within the same invocation of the function, so they share access to the variable i. When constfuncs() returns, the value of the variable i is 10, and all 10 closures share this value. Therefore, all the functions in the returned array of functions return the same value.

Like most modern programming languages, JavaScript uses lexical scoping. This means that functions are executed using the variable scope that was in effect when they were defined, not the variable scope that is in effect when they are invoked.

In order to implement lexical scoping, the internal state of a JavaScript function object must include not only the code of the function but also a reference to the current scope chain.

A combination of a function object and a scope (a set of variable bindings) in which the function’s variables are resolved is called a closure.

Technically, all JavaScript functions are closures: they are objects, and they have a scope chain associated with them.

Dynamically generating graphics from real-time data uses a lot of CPU cycles.

The above code snippet returns the value in scope.

The fundamental rule of lexical scoping is that the JavaScript functions are executed using the scope chain that was in effect when they were defined.

The opposite approach to the lexical scoping is the dynamic scoping.

Dynamic scoping creates variables that can be called from outside the block of code in which they are defined. A variable declared in this fashion is sometimes called a public variable.

Lexical scoping is standardized in all algorithmic languages (ALGOL), such as Ada, Pascal, and Modula2. Additionally, it is used in modern functional languages like ML and Haskel.

All of the mentioned is the correct answer to “Consider the following code snippet : if ( !a [ i ]) continue ; What is the observation made”. This question is standard in competitive examination syllabi for Array And Function.

Returns [1,2,3] is the correct answer to “Consider the following code snippet : var a = [ 1 , 2 , 3 , 4 , 5 ] ; a . slice ( 0 , 3 ) ; What is the possible output for the above code snippet”. This question is standard in competitive examination syllabi for Array And Function.

inject and fold is the correct answer to “The reduce and reduceRight methods follow a common operation called”. This question is standard in competitive examination syllabi for Array And Function.

Few functions return values by default is the correct answer to “Do functions in JavaScript necessarily return a value”. This question is standard in competitive examination syllabi for Array And Function.

The first line results in a real boolean value whereas the second line merely checks for the existence of the objects is the correct answer to “What is the difference between the two lines given below ? !!( obj1 && obj2 ) ; ( obj1 && obj2 ) ;”. This question is standard in competitive examination syllabi for Array And Function.