string.match

str.match(regexp)

var str = 'For more information, see Chapter 3.4.5.1';
var re = /see (chapter \d+(\.\d)*)/i;
var found = str.match(re);

console.log(found);

// logs [ 'see Chapter 3.4.5.1',
//        'Chapter 3.4.5.1',
//        '.1',
//        index: 22,
//        input: 'For more information, see Chapter 3.4.5.1' ]

// 'see Chapter 3.4.5.1' is the whole match.
// 'Chapter 3.4.5.1' was captured by '(chapter \d+(\.\d)*)'.
// '.1' was the last value captured by '(\.\d)'.
// The 'index' property (22) is the zero-based index of the whole match.
// The 'input' property is the original string that was parsed.

var str = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz';
var regexp = /[A-E]/gi;
var matches_array = str.match(regexp);

console.log(matches_array);
// ['A', 'B', 'C', 'D', 'E', 'a', 'b', 'c', 'd', 'e']

var str = "Nothing will come of nothing.";

str.match();   // returns [""]

var str1 = "NaN means not a number. Infinity contains -Infinity and +Infinity in JavaScript.",
    str2 = "My grandfather is 65 years old and My grandmother is 63 years old.",
    str3 = "The contract was declared null and void.";
str1.match("number"); ? // "number" is a string. returns ["number"]
str1.match(NaN); ?      // the type of NaN is the number. returns ["NaN"]
str1.match(Infinity); ? // the type of Infinity is the number. returns ["Infinity"]
str1.match(+Infinity); ?// returns ["Infinity"]
str1.match(-Infinity); ?// returns ["-Infinity"]
str2.match(65); ?       // returns ["65"]
str2.match(+65); ?      // A number with a positive sign. returns ["65"]
str3.match(null); ?     // returns?["null"]