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I'm stuck on sequential string generation, the last iteration of the code below, is trying to return ac.

var charcode = 'abcdefghijklmnopqrstuvwxyz0123456789_';
var arr = [];
var len = 1;
var current = 0;

for(var i = 0; i < 40; i++) {
    if(current == charcode.length) {
        current = 0
        len++
    }
    var tmpStr = ''
    for(var l = 0; l < len; l++) {
        tmpStr = tmpStr + charcode[current];
    }
    console.log(tmpStr)
    current++
}

However, it produces cc.

Sorry, somehow deleted the intended output

a, b, c ... aa, ab, ac ... ba, bc, bb ... ∞

My current understanding suggests within the l < len loop I should check if len > 1 and if so break out and loop for the current charcode[x] but I just can't wrap my head around breaking in and out as it grows.

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2
  • 2
    What is the intended output ? Commented Feb 5, 2016 at 23:22
  • @naomik, updated - my mistake. Commented Feb 5, 2016 at 23:30

2 Answers 2

Reset to default
3

You can do it like this:

var charcode = 'abcdefghijklmnopqrstuvwxyz0123456789_';
var arr = [];
var len = 0;
var current = 0;

for(var i = 0; i < 40; i++) {
  if(current == charcode.length) {
     current = 0;
     len++;
  }

  var tmpStr = (len===0) ? '' : charcode[len-1];

  tmpStr = tmpStr + charcode[current];
  current++;
  console.log(tmpStr);
}

In brief, you didn't need a second loop, but an iteration instead (which is achieved through charcode[len-1]).

JS Bin here.

UPDATE

If you need a continuos loop until the very end of the charset, you can use this:

This one introduces a third variable (digits) to the iteration and choses a .substr() instead of a single character out of the charset, so that everytime the end of the charset is reached, another digit will be added. The variable called x sets the limit. I have tried 4000 and it looks like it is working.

var charcode = 'abcdefghijklmnopqrstuvwxyz0123456789_',
    arr = [],
    len = 0,
    digits = 2,
    current = 0,
    tmpStr = '';

var x = 4000;

for(var i=0; i<x; i++) {
    if(current === charcode.length) {
        current = 0;
        len++;
        if(tmpStr.substr(0,1) === charcode.substr(-digits,1) || tmpStr === charcode.substr(-1) + '' + charcode.substr(-1)) {
            len = 1;
            digits++;
        }  
     }

     if(digits === charcode.length) {
         console.log(charcode);
         console.log(i + ' results found');
         break;
     }

     tmpStr = (len===0) ? '' : charcode.substr([len-1], digits-1);

     tmpStr += charcode[current];
     current++;
     console.log(tmpStr);
}

Final JS Bin here.

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4 Comments

I should have said, this should be continuous, limited by the initial for loops i < x - which is why I was thinking another for loop or self looping function would be needed.
@brod I should have guessed that. :)
Up voting because you provided a solution to the question as originally written.
@brod I made another update. Thank you for accepting it, but the previous solution had some flaws. Take a look at the new update (and the final JS Bin). I think this one is exactly what you were looking for.
1

Unless I'm failing to understand your question, which is highly likely, functional programming solves this problem in an incredibly easy way

const stringSequence = xs =>
  flatMap (x => map (add (x)) (xs)) (xs);

let chars = 'abcdefghijklmnopqrstuvwxyz0123456789_'
console.log (stringSequence (chars));
// ["aa","ab","ac","ad","ae","af","ag","ah","ai","aj","ak","al","am","an","ao","ap","aq","ar","as","at","au","av","aw","ax","ay","az","a0","a1","a2","a3","a4","a5","a6","a7","a8","a9","a_","ba","bb","bc","bd","be","bf","bg","bh","bi","bj","bk","bl","bm","bn","bo","bp","bq","br","bs","bt","bu","bv","bw","bx","by","bz","b0","b1","b2","b3","b4","b5","b6","b7","b8","b9","b_","ca","cb","cc","cd","ce","cf","cg","ch","ci","cj","ck","cl","cm","cn","co","cp","cq","cr","cs","ct","cu","cv","cw","cx","cy","cz","c0","c1","c2","c3","c4","c5","c6","c7","c8","c9","c_","da","db","dc","dd","de","df","dg","dh","di","dj","dk","dl","dm","dn","do","dp","dq","dr","ds","dt","du","dv","dw","dx","dy","dz","d0","d1","d2","d3","d4","d5","d6","d7","d8","d9","d_","ea","eb","ec","ed","ee","ef","eg","eh","ei","ej","ek","el","em","en","eo","ep","eq","er","es","et","eu","ev","ew","ex","ey","ez","e0","e1","e2","e3","e4","e5","e6","e7","e8","e9","e_","fa","fb","fc","fd","fe","ff","fg","fh","fi","fj","fk","fl","fm","fn","fo","fp","fq","fr","fs","ft","fu","fv","fw","fx","fy","fz","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9","f_","ga","gb","gc","gd","ge","gf","gg","gh","gi","gj","gk","gl","gm","gn","go","gp","gq","gr","gs","gt","gu","gv","gw","gx","gy","gz","g0","g1","g2","g3","g4","g5","g6","g7","g8","g9","g_","ha","hb","hc","hd","he","hf","hg","hh","hi","hj","hk","hl","hm","hn","ho","hp","hq","hr","hs","ht","hu","hv","hw","hx","hy","hz","h0","h1","h2","h3","h4","h5","h6","h7","h8","h9","h_","ia","ib","ic","id","ie","if","ig","ih","ii","ij","ik","il","im","in","io","ip","iq","ir","is","it","iu","iv","iw","ix","iy","iz","i0","i1","i2","i3","i4","i5","i6","i7","i8","i9","i_","ja","jb","jc","jd","je","jf","jg","jh","ji","jj","jk","jl","jm","jn","jo","jp","jq","jr","js","jt","ju","jv","jw","jx","jy","jz","j0","j1","j2","j3","j4","j5","j6","j7","j8","j9","j_","ka","kb","kc","kd","ke","kf","kg","kh","ki","kj","kk","kl","km","kn","ko","kp","kq","kr","ks","kt","ku","kv","kw","kx","ky","kz","k0","k1","k2","k3","k4","k5","k6","k7","k8","k9","k_","la","lb","lc","ld","le","lf","lg","lh","li","lj","lk","ll","lm","ln","lo","lp","lq","lr","ls","lt","lu","lv","lw","lx","ly","lz","l0","l1","l2","l3","l4","l5","l6","l7","l8","l9","l_","ma","mb","mc","md","me","mf","mg","mh","mi","mj","mk","ml","mm","mn","mo","mp","mq","mr","ms","mt","mu","mv","mw","mx","my","mz","m0","m1","m2","m3","m4","m5","m6","m7","m8","m9","m_","na","nb","nc","nd","ne","nf","ng","nh","ni","nj","nk","nl","nm","nn","no","np","nq","nr","ns","nt","nu","nv","nw","nx","ny","nz","n0","n1","n2","n3","n4","n5","n6","n7","n8","n9","n_","oa","ob","oc","od","oe","of","og","oh","oi","oj","ok","ol","om","on","oo","op","oq","or","os","ot","ou","ov","ow","ox","oy","oz","o0","o1","o2","o3","o4","o5","o6","o7","o8","o9","o_","pa","pb","pc","pd","pe","pf","pg","ph","pi","pj","pk","pl","pm","pn","po","pp","pq","pr","ps","pt","pu","pv","pw","px","py","pz","p0","p1","p2","p3","p4","p5","p6","p7","p8","p9","p_","qa","qb","qc","qd","qe","qf","qg","qh","qi","qj","qk","ql","qm","qn","qo","qp","qq","qr","qs","qt","qu","qv","qw","qx","qy","qz","q0","q1","q2","q3","q4","q5","q6","q7","q8","q9","q_","ra","rb","rc","rd","re","rf","rg","rh","ri","rj","rk","rl","rm","rn","ro","rp","rq","rr","rs","rt","ru","rv","rw","rx","ry","rz","r0","r1","r2","r3","r4","r5","r6","r7","r8","r9","r_","sa","sb","sc","sd","se","sf","sg","sh","si","sj","sk","sl","sm","sn","so","sp","sq","sr","ss","st","su","sv","sw","sx","sy","sz","s0","s1","s2","s3","s4","s5","s6","s7","s8","s9","s_","ta","tb","tc","td","te","tf","tg","th","ti","tj","tk","tl","tm","tn","to","tp","tq","tr","ts","tt","tu","tv","tw","tx","ty","tz","t0","t1","t2","t3","t4","t5","t6","t7","t8","t9","t_","ua","ub","uc","ud","ue","uf","ug","uh","ui","uj","uk","ul","um","un","uo","up","uq","ur","us","ut","uu","uv","uw","ux","uy","uz","u0","u1","u2","u3","u4","u5","u6","u7","u8","u9","u_","va","vb","vc","vd","ve","vf","vg","vh","vi","vj","vk","vl","vm","vn","vo","vp","vq","vr","vs","vt","vu","vv","vw","vx","vy","vz","v0","v1","v2","v3","v4","v5","v6","v7","v8","v9","v_","wa","wb","wc","wd","we","wf","wg","wh","wi","wj","wk","wl","wm","wn","wo","wp","wq","wr","ws","wt","wu","wv","ww","wx","wy","wz","w0","w1","w2","w3","w4","w5","w6","w7","w8","w9","w_","xa","xb","xc","xd","xe","xf","xg","xh","xi","xj","xk","xl","xm","xn","xo","xp","xq","xr","xs","xt","xu","xv","xw","xx","xy","xz","x0","x1","x2","x3","x4","x5","x6","x7","x8","x9","x_","ya","yb","yc","yd","ye","yf","yg","yh","yi","yj","yk","yl","ym","yn","yo","yp","yq","yr","ys","yt","yu","yv","yw","yx","yy","yz","y0","y1","y2","y3","y4","y5","y6","y7","y8","y9","y_","za","zb","zc","zd","ze","zf","zg","zh","zi","zj","zk","zl","zm","zn","zo","zp","zq","zr","zs","zt","zu","zv","zw","zx","zy","zz","z0","z1","z2","z3","z4","z5","z6","z7","z8","z9","z_","0a","0b","0c","0d","0e","0f","0g","0h","0i","0j","0k","0l","0m","0n","0o","0p","0q","0r","0s","0t","0u","0v","0w","0x","0y","0z","00","01","02","03","04","05","06","07","08","09","0_","1a"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Oh but you don't have flatMap? Easy, just make your own, as well as any other simple procedures that describe the computations you would like to perform

const add = x => y => x + y;

const map = f => xs =>
  Array.prototype.map.call(xs, x => f (x));

const reduce = f => i => xs =>
  Array.prototype.reduce.call(xs, (x,y) => f (x) (y));

const concat = xs => x =>
  xs.concat(x);

const flatMap = f => xs => 
  reduce (concat) ([]) (map (f) (xs));

These procedures are highly reusable and free you from the shackles of imperative code that looks like this

var charcode = 'abcdefghijklmnopqrstuvwxyz0123456789_';
// setup several state variables
var arr = [];
var len = 1; // 6 months later, why did we initialize len at 1?
var current = 0;

// manual looping, with arbitrary static input of 40 (why 40?)
for(var i = 0; i < 40; i++) {
    // logic with potential for human error
    if(current == charcode.length) {
        // variable mutations
        current = 0
        len++
    }
    // temporary variables
    var tmpStr = ''
    // move manual looping
    for(var l = 0; l < len; l++) {
        // more variable mutation
        tmpStr = tmpStr + charcode[current];
    }
    // IO side effects
    console.log(tmpStr)
    // manual iteration
    current++
}
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