A simple fluent validator using Proxy

validator-proxy.js

var proxyContext = function(ctx) {
    return new Proxy(ctx, {
        get(obj, prop) {
            if (prop in obj) {
                return obj[prop];
            }
            const newCtx = proxyContext(ctx.clone());
            if (prop in rules) {
                let re = newCtx.addRule(rules[prop]);
                return re;
            }
        }
    })
}

class Context {
    constructor(rules = []) {
        this.rules = rules;
    }
    addRule(rule) {
        return (...args) => {
            this.rules.push(rule.apply(this, args));
            return this;
        }
    }
    test (value) {
        let result = true;
        for(let i = 0; i < this.rules.length; i++) {
            result = this.rules[i](value);
            if(!result) return result;
        }
        return result;
    }
    clone() {
        return new Context(this.rules.slice());
    }
}
var a = new Context();

var validation = () => {
    return proxyContext(a);
}

var rules = {
    exact (target) {
        return value => value === target;
    },
    equal (target) {
        return value => value == target;
    },
    minLength (len) {
        return value => value.length >= len
    },
    startWith(target) {
        return value => value[0] === target
    }
}

var result2 = validation().minLength(6).startWith('h').test('huruji');
console.log(result2);