SOURCE

let obj ={
    "stepInfo": {
        "companyChannel": [
            "1",
            "2",
            "3"
        ],
        "promotionSteps": [
            {
                "companyFirstChargeAmount": 12,
                "companyFirstChargeAmount1": 122,
                "mainStep": true,
                "returnBcoupon": [
                    {
                        "fastCarBatchId": "1228",
                        "fastCarNumber": 124,
                        "batchId": "11",
                        "number": 129,
                        "replaceFastCarCoupon": 1
                    },
                    {
                        "batchId": "1234"
                    }
                ],
                "sms": {
                    "templateId":"11"
                },
            }
        ],
        "stepCrowdTag": "1001271955"
    }
}
function test(obj){
    Object.keys(obj).map(item=>{
         if(obj[item] && obj[item].constructor === Object){
             obj[item][item] = true
             console.log(obj[item])
         }
    })
}

test(obj)

[
    {
        "stepInfo_companyChannel": ""
    },
    {
        "stepInfo_promotionSteps<0>_mainStep": true
    },
    {
        "stepInfo_promotionSteps<0>_minAmount": 100
    },
    {
        "stepInfo_promotionSteps<0>_maxAmount": 200
    },
    {
        "stepInfo_promotionSteps<1>_mainStep": true
    },
    {
        "stepInfo_promotionSteps<1>_minAmount": 200
    },
    {
        "stepInfo_promotionSteps<1>_returnBcoupon<0>_batchId": 10
    },
    {
        "stepInfo_promotionSteps<1>_returnBcoupon<0>_number": 72
    },
    {
        "stepInfo_promotionSteps<1>_returnBcoupon<0>_replaceFastCarCoupon": 1
    },
    {
        "stepInfo_promotionSteps<1>_returnBcoupon<0>_fastCarBatchId": 25
    },
    {
        "stepInfo_promotionSteps<1>_returnBcoupon<0>_fastCarNumber": 29
    },
    {
        "stepInfo_promotionSteps<1>_returnBcoupon": true
    },
    {
        "stepInfo_promotionSteps<2>_mainStep": true
    },
    {
        "stepInfo_promotionSteps<2>_minAmount": 300
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<0>_batchId": 10
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<0>_number": 72
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<0>_replaceFastCarCoupon": 1
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<0>_fastCarBatchId": 25
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<0>_fastCarNumber": 29
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<1>_batchId": 10
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<1>_number": 72
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<1>_replaceFastCarCoupon": 1
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<1>_fastCarBatchId": 25
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<1>_fastCarNumber": 29
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<2>_batchId": 10
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<2>_number": 72
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<2>_replaceFastCarCoupon": 1
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<2>_fastCarBatchId": 25
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon<2>_fastCarNumber": 29
    },
    {
        "stepInfo_promotionSteps<2>_returnBcoupon": true
    },
    {
        "stepInfo_promotionSteps": true
    },
    {
        "stepInfo": true
    }
]