sort a object array with string attributes

sort_by_attrs.js

const arr = [{attr:'x', value: 2}, {attr:'y', value: 2}, {attr:'z', value: 1}];

// descend
arr.sort((a,b,x='attr')=>+(a[x]<b[x])-+(a[x]>b[x]));
console.log(arr.slice(0));

// ascend
arr.sort((a,b,x='attr')=>+(a[x]>b[x])-+(a[x]<b[x]));
console.log(arr.slice(0));

// multiple attributes descend
arr.sort((a,b,l=['value','attr'])=>l.reduce((r,x)=>r||(+(a[x]<b[x])-+(a[x]>b[x])),0));
console.log(arr.slice(0));

// multiple attributes ascend with order customized
arr.sort((a,b,l=['value','attr'],dir={'attr':-1})=>l.reduce((r,x)=>r||(dir[x]||1)*(+(a[x]>b[x])-+(a[x]<b[x])),0));
console.log(arr.slice(0));