A simple JavaScript function get_integer_from_string() that will convert an input string to an integer, and return all integers found in that string WITHOUT using any built-in library functions like parseInt() and Number(). Return 0 if no numerical sequence is found.

gistfile1.js

function get_integer_from_string(str)
{
    var result = 0,strint = (str.match(/\d/g)!==null)? result = str.match(/\d/g).join("")*1:result=0;
    return result;
}

get_integer_from_string("100"); // returns 100
get_integer_from_string("100abc"); // returns 100
get_integer_from_string("100abc123"); // returns 100123
get_integer_from_string("1a0b0c1d2e3"); // returns 100123
get_integer_from_string("abc"); // returns 0