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JavaScript Questions & Answers – Pattern Matching and Regular Expressions | JavaScript MCQs

(1) The ‘$’ present in the RegExp object is called a ____________
[A] character
[B] matcher
[C] metacharacter
[D] metadata
Answer: metacharacter
(2) Consider the following JavaScript statement containing regular expressions and check if the pattern matches?
var text = "testing: 1, 2, 3"; 
var pattern = /\d+/g;
[A] text==pattern
[B] text.equals(pattern)
[C] text.test(pattern)
[D] pattern.test(text)
Answer: pattern.test(text)

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(3) The regular expression to match any one character not between the brackets is __________
[A] […]
[B] [^]
[C] [^…]
[D] [\D]
Answer: [^…]
(4) What does /[^(]* regular expression indicate?
[A] Match one or more characters that are not open parenthesis
[B] Match zero or more characters that are open parenthesis
[C] Match zero or more characters that are not open parenthesis
[D] Match one or more characters that are open parenthesis
Answer: Match zero or more characters that are not open parenthesis
(5) What will be the result when non greedy repetition is used on the pattern /a+?b/?
[A] Matches the letter b preceded by the fewest number of a’s possible
[B] Matches the letter b preceded by any number of a
[C] Matches letter a preceded by letter b, in the stack order
[D] Matches letter a present in the string
Answer: Matches the letter b preceded by the fewest number of a’s possible
(6) What does the subexpression /java(script)?/ result in?
[A] It matches “java” followed by the optional “script”
[B] It matches “java” followed by any number of “script”
[C] It matches “java” followed by a minimum of one “script”
[D] It matches “java” followed by a single “script”
Answer: It matches “java” followed by the optional “script”
(7) What is the most essential purpose of parentheses in regular expressions?
[A] Define pattern matching techniques
[B] Define subpatterns within the complete pattern
[C] Define portion of strings in the regular expression
[D] matching the complete string
Answer: Define subpatterns within the complete pattern
(8) The method that performs the search-and-replace operation to strings for pattern matching is _______
[A] searchandreplace()
[B] add()
[C] edit()
[D] replace()
Answer: replace()
(9) What would be the result of the following statement in JavaScript using regular expression methods?
[A] Returns [“123″”456″”789”]
[B] Returns [“123″,”456″,”789”]
[C] Returns [1,2,3,4,5,6,7,8,9]
[D] Throws an exception
Answer: Returns [“123″,”456″,”789”]
(10) What will be the purpose of exec() in the following JavaScript code?
var pattern = /Java/g;
    var text = "JavaScript is more fun than Java!";
    var result;
    while ((result = pattern.exec(text)) != null) 
    {
        alert("Matched '" + result[0] + "'" +" at position " + result.index +"; 
              next search begins at " + pattern.lastIndex);
    }
[A] Returns the same kind of array whether or not the regular expression has the global g flag
[B] Returns different arrays in the different turns of iterations
[C] Return a sub part of the array
[D] Returns a null value
Answer: Returns the same kind of array whether or not the regular expression has the global g flag
(11) What will be the output of the following JavaScript code?
System.out.println(Pattern.matches("[amn]", "abcd"));
[A] true
[B] false
[C] undefined
[D] a
Answer: false
(12) What will be the output of the following JavaScript code?
System.out.println(Pattern.matches("[amn]?", "a"));
[A] true
[B] false
[C] undefined
[D] bcd
Answer: true
(13) What will be the output of the following JavaScript code?
System.out.println(Pattern.matches("\\d", "1"));
[A] true
[B] false
[C] undefined
[D] 1
Answer: true
(14) What will be the output of the following JavaScript code?
 System.out.println(Pattern.matches("[adf]+", "a"));
[A] true
[B] false
[C] undefined
[D] 0
Answer: true
(15) What will be the output of the following JavaScript code?
 System.out.println(Pattern.matches("[^abc]", "aemngq"));
[A] true
[B] false
[C] undefined
[D] 1
Answer: false

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