[ruslan_mart]

var rew = 5;
alert( [1, 5, 6, 20, 78, 300].indexOf(rew) + 1 ? 'ok' : 'no' );

var rew = 5;
alert( ~[1, 5, 6, 20, 78, 300].indexOf(rew) ? 'ok' : 'no' );

var rew = 5;
alert( new Set([1, 5, 6, 20, 78, 300]).has(rew) ? 'ok' : 'no' );