Knuth–Morris–Pratt algorithm's javascript implementation in 123 characters.

KMP.js

p = "AABA"			// pattern
t = "AABAACAADAABAAABAA"	// text
m = p.length
n = t.length;
L = [];x=m;while(x--)L.push(0)	// LPS array of size m, initialized to 0
e = [];				// array to store ending indices of the pattern-match in the text

// Knuth–Morris–Pratt algorithm
for(i=1,l=0;i<m;)p[i]==p[l]?L[i++]=++l:l>0?l=L[l-1]:++i;for(i=j=0;i<n;++i)p[j]==t[i]?++j==m?e.push(i):0:j>0&&i--?j=L[j-1]:0

// Print starting positions of pattern-matches in text
for(i=0;i<e.length;++i)
	console.log(e[i]+1-m)