Function isData

docs/app/js/sanddance-app.js:148151–148151

(_)

const outerExpr = (_)=>_ && _.expr;
const outerField = (_)=>_ && _.field;
const isData = (_)=>_ === "data";
const isExpr = (_)=>_ === "expr";
const isField = (_)=>_ === "field";
const isCompare = (_)=>_ === "compare";