minimun-distance.js

//var arr = [ 7, 1, 3, 4, 1, 7 ];
//var arr = [1, 2, 3, 4, 10];
//var arr = [20,760,143,550,365,559,539,299,160,955,706,462,329,786,989,867,47,648,171,369,625,975,538,532,973,25,515,395,724,487,618,745,247,113,647,612,24,186,263,537,493,321,999,174,108,988,394,507,988,917,228,613,892,118,497,218,144,13,613,220,500,583,965,748,49,613,712,73,151,976,610,997,297,961,171,757,949,565,616,937,483,844,903,727,963,400,945,459,765,910,31,266,494,997,366,895,962,78,968,465,406,931,814,56,892,338,813,194,255,782,483,90,626,386,818,941,139,115,752,904,26,784,522,872,133,888,767,447,967,87,264,725,370,79,781,263,417,947,809,672,729,292,763,355,31,933,649,522,48,401,426,426,537,301,650,670,189,769,469,508,857,734,234,227,813,15,842,582,314,651,606,43,296,721,751,679,654,400,201,55,153,979,481,691,280,484,713,470,253,183,978,462,269,564,690,434,580,884,16,894,536,622,290,184,696,41,863,350,441,64,757,946,395,239,989,676,75,703,498,328,238,828,791,507,393,833,941,325,717,309,571,605,283,861,141,979,902,4,682,695,420,439,642,816,30,631,844,105,686,342,786,276,170,577,135,915,762,428,240,831,737,812,437,373,673,930,352,928,935,34,623,707,826,617,523,856,601,719,314,287,413,100,916,584,677,51,499,791,480,92,622,569,904,411,942,577,342,647,857,629,33,481,336,859,450,212,716,51,931,30,691,345,130,607,281,159,10,132,302,490,224,924,60,480,336,354,410,30,1,267,659,35,100,347,894,551,911,962,602,195,344,293,892,474,252,173,985,263,657,639,105,234,564,165,714,252,872,124,634,873,744,293,908,844,992,803,395,904,765,998,99,462,643,991,936,248,516,274,863,525,913,968,759,829,486,826,81,358,302,67,231,46,360,140,891,705,295,286,609,412,636,60,874,632,403,163,232,919,789,95,796,54,63,556,884,901,734,317,259,36,385,491,83,97,983,326,154,630,964,763,42,953,175,269,585,578,432,817,849,573,264,998,627,327,906,511,229,640,181,840,676,918,683,111,15,666,789,170,648,754,285,43,707,813,312,644,743,96,813,945,669,77,943,296,404,849,160,985,489,693,826,517,611,509,981,978,528,770,148,528,524,786,571,583,951,883,227,694,979,40];
var arr = [1, 1];
var result = [];

arr.reduce(function (acc, item, index) {
  if (typeof acc[item] === 'undefined') {
    acc[item] = index;    
    return acc;
  }

  var distance = Math.abs(acc[item] - index)
  result.push(distance);

  return acc;
}, {})


console.log(result)
console.log(Math.min.apply(Math, result));