let arr=[1,true,3]; a.includes(1) //=>true; a.includes(11) //=>false;
indexOfqu
let a=[1,2,3,NaN]; a.includes(1) //=>0 a.indexOf(11) //=>-1
includes认为NaN与自身相等。
let a=[1,2,3,NaN]; a.includes(NaN) //=>true a.indexOf(NaN) //=>-1