Vue源码之 $set

on: {
    "input": function($event) {
        if ($event.target.composing) return;
        $set(obj, "name", $event.target.value)
    }
}

function set (target, key, val) {
        if (isUndef(target) || isPrimitive(target)
        ) {
            warn(("Cannot set reactive property on undefined, null, or primitive value: " + ((target))));
        }
        if (Array.isArray(target) && isValidArrayIndex(key)) {
            target.length = Math.max(target.length, key);
            target.splice(key, 1, val);
            return val
        }
        if (key in target && !(key in Object.prototype)) {
            target[key] = val;
            return val
        }
        var ob = (target).__ob__;
        if (target._isVue || (ob && ob.vmCount)) {
            warn(
                ‘Avoid adding reactive properties to a Vue instance or its root $data ‘ +
                ‘at runtime - declare it upfront in the data option.‘
            );
            return val
        }
        if (!ob) {
            target[key] = val;
            return val
        }
        defineReactive$$1(ob.value, key, val);
        ob.dep.notify();
        return val
    }